Question

A boy imagined a four digit multiple of 5 with different digits. If the first digit is erased, the obtained number is multiple of 9. If the second digit is erased, the obtained number is multiple of 11. If the third digit is erased, the obtained number is multiple of 7. What number a boy imagined?​

Answer 1

Answer:

Since the number is divisible by 3, the sum of the digits should be multiple of 3.

∴The digits can be 0,2,4,6 or 0,4,6,8

Hence the required no. of numbers =(4!−3!)+(4!−3!)=36

Answer 2

Answer:

36

Explanation:

Since the number is divisible by 3, the sum of the digits should be multiple of 3.  

∴The digits can be 0,2,4,6 or 0,4,6,8  

Hence the required no. of numbers =(4!−3!)+(4!−3!)=36  

(0 cannot come in 1st position.)