The original quantity is 20 and the new quantity is 15. Adam incorrectly says the percent decrease is about 14.29%. What is the correct percent decrease? What error did Adam likely make when finding the percent decrease? The correct percent decrease is 25 25%. What error did Adam likely make? A. divided the difference of the two quantities by the sum of the two quantities. B. divided the difference of the two quantities by the product of the two quantities. C. divided the difference of the two quantities by the new quantity. D. divided the new quantity by the original quantity.

A. divided the difference of the two quantities by the sum of the two quantities.

Explanation:

The difference of the quantities is 20-15 = 5

The sum of the quantities is 20+15 = 35

Dividing those results leads to 5/35 = 0.142857 which rounds to 0.1429

That converts to 14.29%

This is likely the path Adam took. This path is incorrect. The correct steps are shown below

Difference = 20-15 = 5

Divide the difference over the original quantity

5/20 = 1/4 = 0.25 = 25%

We have a 25% decrease because the new quantity (15) is smaller than the old quantity (20)

Here's another way to approach the problem

A = old value = 20

B = new value = 15

C = percent change

C = [ (B-A)/A ] * 100%

C = [ (15-20)/20 ] * 100%

C = (-5/20)*100%

C = -0.25*100%

C = -25%

The negative C value means we have a negative percent change, ie we have a percent decrease. So this is another way to get a 25% decrease.

answer: c, the green line

step-by-step explanation:

there is no black line, eliminate b.

simple interest implies periodic payments, but the red line shows no payments, eliminate d.

simple interest has equal payments. if paid say every day, the graph is about a straight line (actually a stairstep).

the yellow line is not straight, eliminate a.

check: the green line is straight, answer is c.

simple interest with positive interest rate gives a straight line sloping up to the right. green line:

g(t) = $100 + ($200-$100) ÷ (20 years) × (t years)

= $100 + (4%/year) × ($100)(t years)

incidentally, the yellow line curving upward represents continuously compounded interest

y = $100 × 2^(t years / (14 assuming the yellow line hits $200 at 14 years. 2^0 is 1, so y(0) = $100; 2^(14/14) is 2, so y(14) = $200.