Katieann16
y varies directly with x, and y = 2 when x = 5.
What is the value of x when y = 15?



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Katieann16
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@jim_thompson5910

jim_thompson5910
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y varies directly with x
so this means
y = kx
where k is some fixed number

jim_thompson5910
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we are told that
y = 2 when x = 5
so
y = kx
2 = k*5
solve for k

Katieann16
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so 6?

jim_thompson5910
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when you solved for k, what did you get

Katieann16
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wait how do i solve for k

jim_thompson5910
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2 = k*5
divide both sides by 5 to isolate k

jim_thompson5910
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k = ???

Katieann16
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2.5?

jim_thompson5910
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you divided in the wrong order

Katieann16
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0.4?

jim_thompson5910
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good,
so
y = kx
turns into
y = 0.4x

jim_thompson5910
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now you want to find x when y = 15, so
y = 0.4x
15 = 0.4x
now solve for x

Katieann16
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37.5?

jim_thompson5910
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you nailed it
you can also represent 37.5 as the fraction 75/2

jim_thompson5910
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so x = 37.5 or x = 75/2

Katieann16
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ok thank you(:

jim_thompson5910
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you're welcome