UPSC Prelims 2025·CSAT·Quantitative Aptitude·Number System

A 4-digit number N is such that when divided by 3, 5, 6, 9 leaves a remainder 1, 3, 4, 7 respectively. What is the smallest value of N?

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Last updated 23 May 2026, 3:31 pm IST
  1. A1068
  2. B1072
  3. C1078Correct
  4. D1082

Explanation

To solve this, we first look at the difference between the divisors and their respective remainders. 3 minus 1 equals 2 5 minus 3 equals 2 6 minus 4 equals 2 9 minus 7 equals 2 Since the difference is a constant 2 in all cases, the number N follows the format: N equals LCM of 3, 5, 6, and 9 minus 2. The LCM of 3, 5, 6, and 9 is 90. Therefore, the general form of the number is 90k minus 2, where k is an integer. To find the smallest 4-digit number, we need 90k to be slightly greater than 1000. If we take k as 12, 90 times 12 equals 1080. N equals 1080 minus 2, which equals 1078. Verification: 1078 divided by 3 leaves remainder 1. 1078 divided by 5 leaves remainder 3. 1078 divided by 6 leaves remainder 4. 1078 divided by 9 leaves remainder 7. The smallest value of N is 1078. Thus, C is the correct option.
Quantitative Aptitude: A 4-digit number N is such that when divided by 3, 5, 6, 9 leaves a remainder 1, 3, 4, 7 respectively. What is the small

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