Question

the sum of the digits of a three digit number is 15. the digit at the tens placecis half of the sum of the digits at the hundred and units places. If 396 is added to the number the digits at the hundred and units places are interchanged. find the number.

Answer 1

let u=units digit
let t=tens digit
let h=hundreds digit
..
h=3u
u+t+h=15
original number: 100h+10t+u
reversed number:100u+10t+h
original number-reversed number=396
(100h+10t+u)-(100u+10t+h)=396
100h+10t+u-100u-10t-h=396
99h-99u=396
99(3u)-99u=396
2u*99=396
u=396/2*99=2
h=3u=6
t=15-t+h=15-8=7
ans:
number: 672