Question

The sum of the digits of a two-digit number is 9. The number is 6 time unit digit . Find the number.​

Answer 1

Let the two digit number be 10x+y

The digits are x and y

x + y = 9.........1

The unit digit number is y

6y = 10x+y...... 2

Solve the equation 2

10x + y - 6y = 0

10x - 5y = 0

Solve

(x + y =9) ×5

10x - 5y = 0

5x + 5y = 45

10x - 5y = 0. 5y gets canceled

15x = 45

x = 45/15

x = 3

Substitute in equation 1

x + y = 9

3 + y = 9

y = 9-3

y = 6

The 2 digit number is 36.

Verification

3 + 6 = 9.......1

6 × 6 = 36......2