Question 908907: The sum of the digits of a certain two-digits number is 7. Reversing its digits increases the number by 9 what is the number ? Answer by MathLover1(20849) (Show Source):
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Let's call the first digit "". Then the second digit must be , so that the two digits add up to .
The value of the original number is ten times the tens digit, plus the units digit (for example, 48 is 4*10+8).
So, the original number is .
When you reverse the digits, you get . If this is greater, then:
Solving this for gives us:
This means the other digit has to be . So the number is .
