Question

The value of y varies directly with x, and y = 5 when x = -20. Find y when x = 35.

Answer 1

Answer:

Step-by-step explanation:

If y= -5 when x= -20  that means x is 4 times y

y=  8.75  when x= 35

Answer 2

Answer:

Our equation is:

$\displaystyle y=-\frac{1}{4}x$

When x=35, y=-35/4 or -8.75.

Step-by-step explanation:

We know that y varies directly with x.

The standard equation is:

$y=kx$

We know that y is 5 when x is -20.

So, let’s substitute 5 for y and -20 for x and solve for k, our constant of variation. So:

$5=k(-20)$

Divide both sides by -20:

$\displaystyle k=-\frac{1}{4}$

Therefore, our constant of variation is -1/4.

Hence, our equation is:

$\displaystyle y=-\frac{1}{4}x$

To find y when x=35, let’s substitute 35 for x. So:

$\displaystyle y=-\frac{1}{4}(35)=-\frac{35}{4}=-8.75$

So, when x=35, y=-8.75.