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20 votes
If y varies directly with x and
y=15 when x is 9, what is x when
y=30?

User Leo Muller
by
8.6k points

2 Answers

9 votes
Answer: 18

Explanation:
Y = Xk
15 = 9k
15/9 =k
30 = 15/9 × X
30/1 ÷ 15/9 =X
30/1 × 9/15 = 270/15

User Crankshaft
by
8.3k points
9 votes

Answer:

x = 18

Explanation:

given y varies directly with x then the equation relating them is

y = kx ← k is the constant of variation

to find k use the condition y = 15 when x = 9 , then

15 = 9x ( divide both sides by 9 )


(15)/(9) = x , that is

x =
(5)/(3)

y =
(5)/(3) x ← equation of variation

when y = 30 , then

30 =
(5)/(3) x ( multiply both sides by 3 to clear the fraction )

90 = 5x ( divide both sides by 5 )

18 = x

User Ameba Spugnosa
by
7.6k points

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