Question

Test whether 1728 is divisible by both 8 and 9​

Answer 1

1728 is divisible by both 8 and 9.

• If the sum of the digits of a number is divisible by 9 then the number will also be completely divisible by 9.

Here, the sum of the digits of 1728 is ( 1+7+2+8) = 18 which is divisible by 9.

∵ 18 ÷ 9 = 2

∴ 1728 is also completely divisible by 9.  1728 ÷ 9 = 192

• If the last 3 digits of a number is completely divisible by 8 or if they are 0 then the number will also be completely divisible by 8.

Here, the last 3 digits of the number is 728 which is completely divisible by 8.

∵ 728 ÷ 8 = 91

∴ 1728 is also completely divisible by 8. 1728 ÷ 8 = 216

Hence proved, 1728 is completely divisible by both 8 and 9.