Question

y varies directly with x. When y = 20, x = 50. Find x when y = 36.
Choose one answer.
a. 75
b. 80
c. 90
d. 105

Answer 1

what do you get?

Answer 2

90 is your answer.

Answer 3

y=kx
20=k(50)
20/50=k
2/5=k
k=2/5

y=2x/5

36=2x/5
5/2 * 36=x
5*36/2=x
5* 18=x
90=x

Answer 4

correct!

Answer 5

thanks guys! thats what i was thinking!

Answer 6

when you see varies think multiplication
when you see inversely think division

Answer 7

uw.

Answer 8

never forget your constant

Answer 9

you can always forget the constant! when you see "varies directly" just look at how the one is varying, and vary the other the same. Here, y goes from 20 to 36, getting multiplied by 1.8 (36/20). So to vary x, we multiply it by 1.8. 50*1.8 = 90.

Answer 10

no you need the constant to find what the constant is lol