SOLUTION: the sum of two numbers is 15. one number is 4 times the other. what are the two numbers

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Question 572221: the sum of two numbers is 15. one number is 4 times the other.
what are the two numbers
Answer by mathsmiles(68) About Me  (Show Source):
You can put this solution on YOUR website!
Let's use X and Y to denote the two numbers we're looking for.
X + Y = 15
X = 4Y

Substitute the 4Y into the first equation for X gives us
(4Y) + Y = 15
5Y = 15 Divide both sides by 5
Y = 3.

One number is 3.

But we know 3 and the other number add to 15. Therefore,
X + 3 = 15
X = 12
So the two numbers are 3 and 12.

Check:
3 + 12 = 15
AND
4 X 3 = 12 Correct!