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4 votes
If f(x) varies directly with x and f(x)=40 when x=8, find the value of f(x) when x=2.

A. 2
B. 5
C. 10
D. 15

2 Answers

2 votes

C

since the quantities vary directly then

x = kf(x) ( where k is the constant of variation )

to find k use the given condition , f(x) = 40 when x = 2

k =
(x)/(f(x)) =
(8)/(40) =
(1)/(5)

thus x =
(1)/(5)f(x)

when x = 2

f(x) =
(x)/(k) =
(2)/((1)/(5) ) = 10


User Emre Koc
by
7.9k points
3 votes

f(x)=40

x=8

so if x=2 it would be 40/8 which is 5

User Philshem
by
7.1k points

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