Question

Instead of raising the number to a second power, he doubled it. His 2 digit answer had the same digits as the correct answer but in reverse order. What was the correct answer

Answer 1

Answer: 81 ==> correct answer

Explanation:

n=number

n^2+n*2=n*11 ==> the sum of a 2 digit number and the reverse of the two digit number is a multiple of 11. For example, 21+12=33. 33/11=3, so 33 is a multiple of 11.

n*n+2n=11n

n(n+2)=11n

n+2=11

n=9

n^2=

9^2=81 ==> correct answer