Question

Replace _ by a digit to make the number divisible by 11. The number is - 439_o87

Answer 1

Dear Student,

Let a be placed in the blank.

Sum of the digits at odd places = 4 + 9 + 0 + 7 = 20

Sum of the digits at even places = 3 + a + 8 = 11 + a

Difference = 11 + a − 20 = a - 9

For a number to be divisible by 11, this difference should be zero or a multiple of 11.

If a - 9 = 0, then

a = 9

or

A closest multiple of 11, which is near to 9, has to be taken. It is 11 itself.

a - 9 = 11

a = 20

However it cannot be a two digit

Therefore, the required digit is 9.

Regards