Question

If y varies inversely as x and y = 107 when x = –15, find y when x = 5. Round your answer to the nearest hundredth, if necessary.

35.67

321

–321

–35.67

Answer 1

-321

Explanation:

We know that x and y varies inversely, and that when y = 107, x = -15

we can represent this in the following table:

y x

107 ⇒ -15

Now we need to know the value of y when x = 5,

y x

107 ⇒ -15

? ⇒ 5

we find the answer by inverse rule of three: multiply the top quantities (107 by -15) and then divide by the remaining amount (5), this is:

107(-15)/5 = -1605/5 = -321

Answer 2

-321

Explanation:

The new value of x is the old value divided by -3. Since y varies inversely, its new value will be the old value divided by 1/-3, equivalently, multiplied by -3:

(-3)(107) = -321