Question

The value of y is directly proportional to the value of x.

If y = 12 when x = 15, what is the value of x when y = 40?
A.
12
B. 32
C.43
D.
50

Answer 1

The value of x when y equals 40 is 50, found by using the directly proportional relationship between x and y and the proportionality constant.

Step-by-step explanation:

The value of y is directly proportional to the value of x. This means if y increases, x will increase by the same proportion, and vice versa. To solve this problem, we use the proportionality constant k. We know that y = 12 when x = 15, so we can find k by using the equation y = kx.

First, let's find k:
12 = k * 15
k = 12 / 15
k = 0.8

Now we can use that k value to find the value of x when y = 40:
y = kx
40 = 0.8x
x = 40 / 0.8
x = 50

Therefore, the value of x when y = 40 is 50.

Answer 2

D

Step-by-step explanation:

Given y is directly proportional to x then the equation relating them is

y = kx ← k is the constant of proportion

To find k use the condition y = 12 when x = 15

12 = 15k ( divide both sides by 15 )

0.8 = k

y = 0.8x ← equation of proportion

When y = 40 , then

40 = 0.8x ( divide both sides by 0.8 )

50 = x → D