Question

If a nine-digit number 785x3678y is divisible by 72, then the value of (x − y) is:

B -2 Correct Answer Incorrect Answer
C -1 Correct Answer Incorrect Answer
D 2 Correct Answer Incorrect Answer

Solution

The nine digit number is 785x3678y is divisible by 72, so we can say number also divisible by 8 and 9. 785x3678y is divisible by 8 if last digit three digit 78y is divisible by 8. 78y is divisible by 8 if y = 4 785x36784 is divisible by 9 if the sum of its digit is divisible by 9. => 7 + 8 + 5 + x + 3 + 6 + 7 + 8 + 4 => 48 + x Put x = 6 => 48 + 6 = 54 As we know, 54 is divisible by 9. Now, x – y = 6 - 4 = 2

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