Question

The total number of four digit numbers such that each of first three digits is divisible by the last digit, is equal to _______.

Answer 1

The correct answer is 1086
Let pqrs is 4-digit number.
So , first 3-digit pqr should be divisible by 's'
If s=1 , then numbers = 9×10×10 = 900
If s=2 , then numbers = 4×5×5 = 100
If s=3, then numbers = 3×4×4 = 48
If s=4, then numbers = 2×3×3 = 18
If s=5, then numbers = 1×2×2 = 4 numbers
If s=6,7,8 and 9 then , numbers = 4×4 = 16
∴ Total 4 digit Number = 900 + 100 + 48 + 18 + 4 + 16 = 1086