Question

The ten’s digit of a two digit number is three times the unit digit. The sum of the number and the unit digit is 32. Find the number.

Answer 1

Let the digit at unit’s place be x and the digit at ten’s place be y.
Required no. = 10y + x

According to the question,
y = 3x 
⇒ 3x - y = 0                       ...(1)
and,
10y + x + x = 32
10y + 2x = 32                    ...(2)

Multiplying equation no. (1) by 10.
30x - 10y = 0                    ....(3)
Now,
Adding equation (3) and (2)
          30x - 10y = 0
     +   2x + 10y = 32  
          32x = 32
             x = 1

From (1), we get
y = 3(1) = 3
Required no is = 10(3) + 1 = 31.