Which of the following integers is divisible by both 3 and 4? — GRE General Test

Which of the following integers is divisible by both $3$ and $4$ ?

72

For an integer to be divisible by both

3

and

4

, it must satisfy the rules for both divisors. For

72

, the sum of the digits is

7 + 2 = 9

, which is divisible by

3

. Additionally,

72 \div 4 = 18

, which is an integer. Thus,

72

is divisible by both

3

and

4

Recall the divisibility rule for 3

An integer is divisible by 3 if the sum of its digits is divisible by 3.

This allows quick evaluation of divisibility by 3.

Recall the divisibility rule for 4

An integer is divisible by 4 if its last two digits form a number divisible by 4.

This allows quick evaluation of divisibility by 4.

Test

72

against both divisibility rules

Sum of digits of

72

7 + 2 = 9

, which is divisible by

3

. Also,

72 \div 4 = 18

, which is an integer.

72

meets both required criteria.

Divisibility Rules for 3 and 4

Estimated Time:45s

Question