Problems based on Numbers Test 4

Question : 10 of 40

Marks: +1, -0

A number consists of two digits whose sum is 8. If 18 is added to the number, the digits are reversed. The number is equal to:

Validate

Solution:

Let the unit digit be = x1Tens digit = 8 - x
Number = 10 (8 - x) + x
= 80 - 10x + x
= 80 - 9x
New number = 10x + 8 - x = 9x + 8
Now, 80 - 9x + 18 = 9x + 8
18 + 80 - 8 = 9x + 9x
18x = 90

x = 90/18

Unit digit x = 5
Tens digit = 8 - 5 = 3
So, the number is 35.

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