Find a 4 - digit odd number using each of the digits 1, 2, 4 and 5 only once such that when the first and the last digits are interchanged, it is divisible by 4.

Question

Philoid · Accepted Answer

A number is divisible by 4 if the number formed by its two last digits is divisible by 4

∴ the possible last two digits of the number formed by interchanging first and last digit of the original number are 12, 24, 52

Choose any (say 52)

Now, original number is odd.

Therefore its last digit = 1

And first digit = 2

Second digit = 4(only 4 is remaining)

Hence, the original number = 2451