Question

if the 8-digit number 789X531y is divisible by 72 then the value of (5x-3y) is​

Answer 1

Here ,

Digit is 789X531Y is divisible by 72

• It means it is also divisible by 8 and 9 .

As we know that :

• For 8 , the last three digit is divisible by 8 .

• For 9 , the sum of all digit is divisible by 9 .

Here , last three digit is 31Y

if we put Y = 2 then it divisible by 8 ..

Now,

sum of digit = 35 + X

if we put X = 1 then it becomes 36 which is divisible by 9 .

So , we get X = 1 and Y = 2

Now. 5x-3y = 5(1)-3(2)= 5 - 6 = -1