as the weight held by a spring increases, the length of the spring increases proportionally. Suppose a 2-lb weight stretches a spring to 15 in., and a 12-lb weight stretches the same spring to 20 in. What is the length of the spring with no weight attached?

How did you get 90?

answer is right

how did he get 90?

Deeeeeez Nutz

To find the length of the spring with no weight attached, we can set up a proportion based on the given information.

Let's denote the length of the spring with no weight attached as "L".

According to the problem, when a 2-lb weight is attached, the length of the spring is 15 inches. And when a 12-lb weight is attached, the length is 20 inches.

We can set up the following proportion:

(2 lb) / (15 in) = (12 lb) / (20 in)

To solve this proportion, we can cross-multiply:

(2 lb) * (20 in) = (12 lb) * (15 in)

40 lb-in = 180 lb-in

Now, divide both sides by 40 lb-in:

L = (180 lb-in) / (40 lb-in)

L = 4.5 inches

Therefore, the length of the spring with no weight attached is 4.5 inches.

(20-x)/(15-x) = 12/2 = 6

90 - 6x = 20 - x
5x = 70
x = 14 inches