Question

The sum of the digits of a 2-digit number is 9. The number is 6 times the units digit. find the number.

Answer 1

The digit in the tens place is x

The digit in the ones place is y

The number is (10x + y)

Form equation 1 :

THE sum of the digits is 9

x + y = 9

x = 9 - y

Form equation 2 :

The number is 6 times the units

10x + y = 6y

Put the two equations together:

x = 9 - y -------------------- [ 1 ]

10x + y = 6y -------------------- [ 2 ]

Find y:

Sub [ 1 ] into [ 2 ]:

10(9 - y) + y = 6y

90 - 10y + y = 6y

90 - 9y = 6y

15y = 90

y = 90 ÷ 15

y = 6

Find x:

When y = 6

x = 9 - 6

x = 3

Find the number

The number = 10x + y

The number = 10(3) + 6

The number = 36