Question

By which of the following numbers is 7538876849 divisible?

• A. 7
• B. 2
• C. 5
• D. 3

Answer 1

The correct option is A 7

Make the number into groups of 3-digits each from right to left. If the left most group is less than 3 digits take it as group.
A = 849 , B = 876, C = 538, D = 7
Now,
Adding A + C and B + D
A + C = 849 + 538 = 1387
B + D = 876 + 7 = 883
Now, subtract 883 from 1387 and check the divisibility rule of 7 for the resultant 3 digit number:
1387 - 883 = 504
So, applying 2a + 3b + c
a = 5, b = 0 and c = 4
$2\times 5$ + $3\times 0$ + 4 = 14
$\therefore$ 14 is divisible by 7
Hence, 7538876849 is divisible by 7.

7538876849 is an odd number, so it is not divisible by 2.

Sum of digits of 7538876849 is 65 which is not divisible by 3. Therefore, 7538876849 is not divisible by 3.

7538876849 doesn't end with either 0 or 5. Therefore, 7538876849 is not divisible by 5.