Question

a number consists of two digits whose sum is 8 if 18 is added to the number 8 digits are reversed find the number

Answer 1

our number is xy, which means 10x+y.

the sum of the 2 digits is 8, so x+y = 8 


if we add 18 to the number, ie 10x+y+18 the result is then yx (ie 10y+x)
--> 10x+y+18 = 10y+x
--> 9x + y + 18 = 10y

--> 9x - 9y + 18 = 0
--> 9x - 9y = -18
--> x - y = -2 

The number is 35

Answer 2

Hi ,

Let units place digit = x

Ten's place digit = 8 - x

Original number = 10( 8 - x ) + x

= 80 - 10x + x

= 80 - 9x ----( 1 )

Reversing the digits we get a new

Number = 10x + 8 - x

= 9x + 8 -----( 2 )

According to the problem given

80 - 9x + 18 = 9x + 8

98 - 8 = 9x + 9x

90 = 18x

90 / 18 = x

x = 5

Therefore ,

Put x = 5 in ( 1 ),

Original number = 80 - 9x

= 80 - 9 × 5

= 80 - 45

= 35

I hope this helps you.

:)