Number Problem 4 Solution

You might be able to figure this out in your head since it doesn't matter if the number was 900, 9 million etc if its a situation that add up to 9 and 1 number is twice as big that you're adding. So what numbers 1 through the number 9 could you add together to get 9? 1 and 8 , 2 and 7, 3 and 6, and 4 and 5. Now which one of these is twice as big as the 1st number? The 6 is twice as big as the 3. But the problem asked for what 2 numbers added up to 900. So just add 2 zeros onto the 6 and 3. 300 and 600 are the answers.

Algebraically,

x = 1st number
2x = 2nd number *2x means the same thing as 2 times x or 2 X x
900 is the number were looking for so..

x + 2x = 900
3x = 900
x = 900/3
x = 300
substituting back in x is 300 and 2x is 2(300) or 2 X 300 which is 600.