Question

Lus

Suppose that y varies directly with x
and y = 10 when x = 20. What is y
when x = 15?
Enter your answer as a simplified fraction.
y =

Answer 1

15/2

Explanation:

y varies directly as x can be written as:

y & x

y = Kx

K = y/x

But from the question, we were told that:

y = 10

X = 20

K = y/x

K = 10/20

K = 1/2

The formula for the expression is:

y = Kx

y = 1/2 x

Now let us solve for y, when:

x = 15

y = 1/2 x

y = 1/2 x 15

y = 15/2

Answer 2

When x = 15, y = 15/2

Explanation:

Formula: "y varies directly with x" comes out to y = kx symbolically.

Find the value of the constant of proportionality, k: If y = 10 when x = 20, then this relationship becomes 10 = 20k, and k = 1/2.

Then the formula is y = (1/2)x.

When x = 15, y = 15/2