Two numbers

We have two numbers. Their sum is 140. One-fifth of the first number is equal to half the second number. Determine those unknown numbers.

Correct answer:

x =  100
y =  40

Step-by-step explanation:


x+y=140
x/5 = y/2

x+y = 140
2x-5y = 0

Pivot: Row 1 ↔ Row 2
2x-5y = 0
x+y = 140

Row 2 - 1/2 · Row 1 → Row 2
2x-5y = 0
3.5y = 140


y = 140/3.5 = 40
x = 0+5y/2 = 0+5 · 40/2 = 100

x = 100
y = 40

Our linear equations calculator calculates it.



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Showing 2 comments:
Math student
I just took x as 40 and y as 100 and it says I'm wrong :(

Dr Math
Please read again: One-fifth of the first number is equal to half the second .... 40/5 is not equal 100/2





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