Question

If y varies directly as x, and y = 25 as x = 5, find y for the x-value 7.
Answer
20
25
35
30

Answer 1

y varies directly as x

means that

y = k*x

Answer 2

it tells us that when x = 5, y = 25

so

y = k*x

y = k*5 ... plug in x =5

25 = k*5 ... plug in y = 25, now solve for k

k = ???

Answer 3

tell me what you get for k

Answer 4

5...?

Answer 5

good, k = 5

Answer 6

so

y = k*x

turns into

y = 5x

Answer 7

now we want to know the value of y when x = 7, so

y = 5x

y = 5*7 ... plug in x = 7

y = ??

Answer 8

35. Thanks I get it now!

Answer 9

correct, yw