Thread: Reverse Digit problem help

I need help on understanding and do a reverse digit problem.

problem is:

If you take two-digit number to make a second two-digit number, and add these numbers together, their sun will be 121. What is the original number??

First number is
Reverse the digits, you get
add the two to get

so you must have . Possible choices (up to reversing the digits) are .

Thanks for the answer and i understand how to do the problem now.

I'm assuming that when you say you "take two-digit number to make a second two-digit number", you make the second number by reversing the digits.

Let x be the first digit, and y be the second digit.

Your first number is x + 10y, so your second number is 10x + y

When you add the two numbers together you have

(x + 10y) + (10x + y) = 10x + x + 10y + y = 11x + 11y = 11(x + y) = 121

So x + y = 11

Remember, x and y represent the digits, so they are single digit numbers.

So, we have:
x y
2 9
3 8
4 7
5 6
6 5
7 4
8 3
9 2

i.e. 29 + 92 = 38 + 83 = 47 + 74 = 56 + 65 = 65 + 56 = 74 + 47 = 83 + 38 = 92 + 29 = 121