Question

Which one of the following numbers is divisible by 9, 11, and 13?

• A. 1286
• B. 1287
• C. 1289
• D. 1283

Answer 1

The Correct Option is B

To check divisibility by 9, 11, and 13, we find the least common multiple (LCM) of 9, 11, and 13. The LCM of 9, 11, and 13 is: \[ LCM(9, 11, 13) = 9 \times 11 \times 13 = 1287 \] Now, check if 1287 is divisible by 9, 11, and 13: \[ 1287 \div 9 = 143, \quad 1287 \div 11 = 117, \quad 1287 \div 13 = 99 \] Thus, 1287 is divisible by all three numbers. To check divisibility by multiple numbers, first find their LCM and check if the given number is divisible by the LCM.