Question

the sum of the digits of a two digit number is 9. the number is 6 times the unit digit. find the number

Answer 1

Let the tens digit = x

The unitis digit =y

⇒ x + y = 9

⇒ x = 9 - y

The value of the number is [10x + y]

⇒ (10x + y) = 6y

Substitute (9 - y) for x in the above

⇒10(9 - y) + y = 6y

⇒90 - 10y + y = 6y

⇒90 - 9y = 6y

⇒90 = 15y   or  y = 90/15

⇒ y = 6

since  x+y = 9

⇒x + 6 = 9

⇒x = 9-6

⇒x = 3

⇒Since x+y = 9,   3+y = 9 and y = 6

⇒tens digit =3 and unit digit =6

So our number is 36 ANS