50 Number System PYQ (Solutions)
Master Number System for CAT 2026 with practice questions and detailed explanations
This topic deals with properties of numbers (integers, remainders, base systems, etc.). It has had a limited presence in CAT.
- CAT 2017: About 4 questions on Number System in each slot.
- CAT 2018: Only 2 questions (out of 34) were from Numbers.
- CAT 2019: 2 questions.
- CAT 2020: At most 1 per slot.
- CAT 2021–2022: 1 or none in most slots.
- CAT 2023: Slight uptick with around 2–3 questions per slot, showing an occasional “spike” in this topic.
In general, Number System is not heavily weighted but remains an essential basic area.
Weightage Over Past Years
| Year | Q.NONumber of questions | Difficulty Level |
|---|---|---|
| 2025 | 7 | Hard |
| 2024 | 5 | Medium |
| 2023 | 5 | Hard |
| 2022 | 6 | Hard |
| 2021 | 4 | Medium |
| 2020 | 8 | Medium |
| 2019 | 3 | Hard |
| 2018 | 6 | Medium |
| 2017 | 6 | Medium |
CAT 2025 Number System questions
Question 1
Slot-1
In a 3-digit number N, the digits are non-zero and distinct such that none of the digits is a perfect square, and only one of the digits is a prime number. Then, the number of factors of the minimum possible value of N is
In a 3-digit number N, the digits are non-zero and distinct such that none of the digits is a perfect square, and only one of the digits is a prime number. Then, the number of factors of the minimum possible value of N is
Question 2
Slot-1
Let and , where is the greatest integer not exceeding . If set represents all feasible values of , then a possible subset of is:
Let and , where is the greatest integer not exceeding . If set represents all feasible values of , then a possible subset of is:
Question 3
Slot-2
The number of divisors of , which are of the form , where is a non-negative integer, is
The number of divisors of , which are of the form , where is a non-negative integer, is
Question 4
Slot-2
Suppose ( a , b , c ) are three distinct natural numbers, such that ( 3 a c = 8 ( a + b ) ). Then, the smallest possible
value of ( 3 a + 2 b + c ) is
Suppose ( a , b , c ) are three distinct natural numbers, such that ( 3 a c = 8 ( a + b ) ). Then, the smallest possible value of ( 3 a + 2 b + c ) is
Question 5
Slot-2
If ( m ) and ( n ) are integers such that ( ( m + 2 n ) ( 2 m + n ) = 27 ), then the maximum
possible value of ( 2 m - 3 n ) is
If ( m ) and ( n ) are integers such that ( ( m + 2 n ) ( 2 m + n ) = 27 ), then the maximum possible value of ( 2 m - 3 n ) is
Question 6
Slot-3
For a 4-digit number (greater than 1000), sum of the digits in the thousands, hundreds, and tens places is 15. Sum of the digits in the hundreds, tens, and units places is 16. Also, the digit in the tens place is 6 more than the digit in the units place. The difference between the largest and smallest possible value of the number is
For a 4-digit number (greater than 1000), sum of the digits in the thousands, hundreds, and tens places is 15. Sum of the digits in the hundreds, tens, and units places is 16. Also, the digit in the tens place is 6 more than the digit in the units place. The difference between the largest and smallest possible value of the number is
Question 7
Slot-3
The sum of all the digits of the number ( \left( 10 ^ { 50 } + 10 ^ { 25 } - 123 \right) ), is
The sum of all the digits of the number ( \left( 10 ^ { 50 } + 10 ^ { 25 } - 123 \right) ), is
CAT 2024 Number System questions
Question 1
Slot-1
For any natural number , let be the largest
integer not exceeding . Then the value of is
For any natural number , let be the largest integer not exceeding . Then the value of is
Question 2
Slot-1
When is divided by 7 , the remainder is
When is divided by 7 , the remainder is
Question 3
Slot-2
When is divided by 11 , the remainder is
When is divided by 11 , the remainder is
Question 4
Slot-2
If and are natural numbers such that , and , then equals
If and are natural numbers such that , and , then equals
Question 5
Slot-3
If is divided by 13 , the remainder is
If is divided by 13 , the remainder is
CAT 2023 Number System questions
Question 1
Slot-1
Let be the least positive integer such that 168 is a factor of . If is the least positive integer such that is a factor of , then equals
Let be the least positive integer such that 168 is a factor of . If is the least positive integer such that is a factor of , then equals
Question 2
Slot-2
Let , , , and be natural numbers such that , , and , ten the largest possible value of is
Let , , , and be natural numbers such that , , and , ten the largest possible value of is
Question 3
Slot-2
The number of positive integers less than 50, having exactly two distinct factors other than 1 and itself, is
The number of positive integers less than 50, having exactly two distinct factors other than 1 and itself, is
Question 4
Slot-2
For any natural numbers , , and , such that divides both and , must be a common divisor of
For any natural numbers , , and , such that divides both and , must be a common divisor of
Question 5
Slot-3
The sum of the first two natural numbers, each having 15 factors (including 1 and the number itself), is
The sum of the first two natural numbers, each having 15 factors (including 1 and the number itself), is
CAT 2022 Number System questions
Question 1
Slot-1
For any real number , let be the largest integer less than or equal to . If then is
For any real number , let be the largest integer less than or equal to . If then is
Question 2
Slot-1
For natural numbers , , and , if and , then what is the minimum possible value of ?
For natural numbers , , and , if and , then what is the minimum possible value of ?
Question 3
Slot-1
Let be the largest positive integer that divides all the numbers of the form , and be the largest positive integer that divides all the numbers of the form , where is any positive integer. Then equals
Let be the largest positive integer that divides all the numbers of the form , and be the largest positive integer that divides all the numbers of the form , where is any positive integer. Then equals
Question 4
Slot-2
For some natural number , assume that ! is divisible by . The largest possible value of is
For some natural number , assume that ! is divisible by . The largest possible value of is
Question 5
Slot-2
The number of integers greater than 2000 that can be formed with the digits 0, 1, 2, 3, 4, 5, using each digit at most once, is
The number of integers greater than 2000 that can be formed with the digits 0, 1, 2, 3, 4, 5, using each digit at most once, is
Question 6
Slot-3
A school has less than 5000 students and if the students are divided equally into teams of either 9 or 10 or 12 or 25 each, exactly 4 are always left out. However, if they are divided into teams of 11 each, no one is left out. The maximum number of teams of 12 each that can be formed out of the students in the school is
A school has less than 5000 students and if the students are divided equally into teams of either 9 or 10 or 12 or 25 each, exactly 4 are always left out. However, if they are divided into teams of 11 each, no one is left out. The maximum number of teams of 12 each that can be formed out of the students in the school is
CAT 2021 Number System questions
Question 1
Slot-1
How many three-digit numbers are greater than 100 and increase by 198 when the three digits are arranged in the reverse order?
How many three-digit numbers are greater than 100 and increase by 198 when the three digits are arranged in the reverse order?
Question 2
Slot-2
For a 4-digit number, the sum of its digits in the thousands, hundreds and tens places is 14, the sum of its digits in the hundreds, tens and units places is 15, and the tens place digit is 4 more than the units place digit. Then the highest possible 4-digit number satisfying the above conditions is
For a 4-digit number, the sum of its digits in the thousands, hundreds and tens places is 14, the sum of its digits in the hundreds, tens and units places is 15, and the tens place digit is 4 more than the units place digit. Then the highest possible 4-digit number satisfying the above conditions is
Question 3
Slot-2
A box has 450 balls, each either white or black, there being as many metallic white balls as metallic black balls. If 40% of the white balls and 50% of the black balls are metallic, then the number of non-metallic balls in the box is
A box has 450 balls, each either white or black, there being as many metallic white balls as metallic black balls. If 40% of the white balls and 50% of the black balls are metallic, then the number of non-metallic balls in the box is
Question 4
Slot-3
In a tournament, a team has played 40 matches so far and won 30% of them. If they win 60% of the remaining matches, their overall win percentage will be 50%. Suppose they win 90% of the remaining matches, then the total number of matches won by the team in the tournament will be
In a tournament, a team has played 40 matches so far and won 30% of them. If they win 60% of the remaining matches, their overall win percentage will be 50%. Suppose they win 90% of the remaining matches, then the total number of matches won by the team in the tournament will be
CAT 2020 Number System questions
Question 1
Slot-1
The mean of all 4 digit even natural numbers of the form 'aabb', where a>0, is
The mean of all 4 digit even natural numbers of the form 'aabb', where a>0, is
Question 2
Slot-1
If a, b and c are positive integers such that ab = 432, bc = 96 and c < 9, then the smallest possible value of a + b + c is
If a, b and c are positive integers such that ab = 432, bc = 96 and c < 9, then the smallest possible value of a + b + c is
Question 3
Slot-1
How many 3-digit numbers are there, for which the product of their digits is more than 2 but less than 7?
How many 3-digit numbers are there, for which the product of their digits is more than 2 but less than 7?
Question 4
Slot-1
Let A, B and C be three positive integers such that the sum of A and the mean of B and C is 5. In addition, the sum of B and the mean of A and C is 7. Then the sum of A and B is
Let A, B and C be three positive integers such that the sum of A and the mean of B and C is 5. In addition, the sum of B and the mean of A and C is 7. Then the sum of A and B is
Question 5
Slot-3
How many of the integers 1, 2, … , 120, are divisible by none of 2, 5 and 7?
How many of the integers 1, 2, … , 120, are divisible by none of 2, 5 and 7?
Question 6
Slot-3
How many integers in the set {100, 101, 102, ..., 999} have at least one digit repeated?
How many integers in the set {100, 101, 102, ..., 999} have at least one digit repeated?
Question 7
Slot-3
Let , and be positive integers such that , and . If , then how many distinct values are possible for ?
Let , and be positive integers such that , and . If , then how many distinct values are possible for ?
Question 8
Slot-3
How many pairs (a,b) of positive integers are there such that a ≤ b and ab = 42017 ?
How many pairs (a,b) of positive integers are there such that a ≤ b and ab = 42017 ?
CAT 2019 Number System questions
Question 1
Slot-2
How many factors of are perfect squares which are greater than 1? [TITA]
How many factors of are perfect squares which are greater than 1? [TITA]
Question 2
Slot-2
How many pairs of positive integers satisfy the equation ?
How many pairs of positive integers satisfy the equation ?
Question 3
Slot-2
In a six-digit number, the sixth, that is, the rightmost, digit is the sum of the first three digits, the fifth digit is the sum of first two digits, the third digit is equal to the first digit, the second digit is twice the first digit and the fourth digit is the sum of fifth and sixth digits. Then, the largest possible value of the fourth digit is [TITA]
In a six-digit number, the sixth, that is, the rightmost, digit is the sum of the first three digits, the fifth digit is the sum of first two digits, the third digit is equal to the first digit, the second digit is twice the first digit and the fourth digit is the sum of fifth and sixth digits. Then, the largest possible value of the fourth digit is [TITA]
CAT 2018 Number System questions
Question 1
Slot-1
The number of integers such that , and is perfectly divisible by either 3 or 4, is [TITA]
The number of integers such that , and is perfectly divisible by either 3 or 4, is [TITA]
Question 2
Slot-1
While multiplying three real numbers, Ashok took one of the numbers as 73 instead of 37. As a result, the product went up by 720. Then the minimum possible value of the sum of squares of the other two numbers is: [TITA]
While multiplying three real numbers, Ashok took one of the numbers as 73 instead of 37. As a result, the product went up by 720. Then the minimum possible value of the sum of squares of the other two numbers is: [TITA]
Question 3
Slot-2
If and are positive integers such that and is an integral multiple of , then the largest possible is
If and are positive integers such that and is an integral multiple of , then the largest possible is
Question 4
Slot-2
How many two-digit numbers, with a non-zero digit in the units place, are there which are more than thrice the number formed by interchanging the positions of its digits?
How many two-digit numbers, with a non-zero digit in the units place, are there which are more than thrice the number formed by interchanging the positions of its digits?
Question 5
Slot-2
If the sum of squares of two numbers is 97, then which one of the following cannot be their product?
If the sum of squares of two numbers is 97, then which one of the following cannot be their product?
Question 6
Slot-2
The smallest integer for which holds, is closest to
The smallest integer for which holds, is closest to
CAT 2017 Number System questions
Question 1
Slot-1
If a, b, c, and d are integers such that a + b + c + d = 30, then the minimum possible value of (a - b)² + (a - c)² + (a - d)² is (TITA)
If a, b, c, and d are integers such that a + b + c + d = 30, then the minimum possible value of (a - b)² + (a - c)² + (a - d)² is (TITA)
Question 2
Slot-1
The number of solutions (x, y, z) to the equation x – y – z = 25, where x, y, and z are positive integers such that x ≤ 40, y ≤ 12, and z ≤ 12 is
The number of solutions (x, y, z) to the equation x – y – z = 25, where x, y, and z are positive integers such that x ≤ 40, y ≤ 12, and z ≤ 12 is
Question 3
Slot-1
An elevator has a weight limit of 630 kg. It is carrying a group of people of whom the heaviest weighs 57 kg and the lightest weighs 53 kg. What is the maximum possible number of people in the group? [TITA]
An elevator has a weight limit of 630 kg. It is carrying a group of people of whom the heaviest weighs 57 kg and the lightest weighs 53 kg. What is the maximum possible number of people in the group? [TITA]
Question 4
Slot-2
Let a₁, a₂, a₃, a₄, a₅ be a sequence of five consecutive odd numbers. Consider a new sequence of five consecutive even numbers ending with 2a₃. If the sum of the numbers in the new sequence is 450, then a₅ is [TITA]
Let a₁, a₂, a₃, a₄, a₅ be a sequence of five consecutive odd numbers. Consider a new sequence of five consecutive even numbers ending with 2a₃. If the sum of the numbers in the new sequence is 450, then a₅ is [TITA]
Question 5
Slot-2
How many different pairs of positive integers are there such that and ?
How many different pairs of positive integers are there such that and ?
Question 6
Slot-2
If the product of three consecutive positive integers is 15600 then the sum of the squares of these integers is
If the product of three consecutive positive integers is 15600 then the sum of the squares of these integers is
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