Question

in a 2 digit number the unit place digit is twice the tens place digit if 27 is added to the number the digits interchange their place. What is the number?

Answer 1

let the ones digit x and tens digit be y
original no = 10 y + x
a/q to question
y = 2x........... (i)
..........10 y +x +.27 = 10x +.y
10 y -y +x -10x = -27
9y -9x = -27
9 (y -x) = 27
(y -x) = 3.......(ii)
y -.x = 3......(putting value of y = 2x)
2x - x = 3
x = 3
y =2x
y = 2 *3 = 6
number = 10 *6 +3
63