Can you please explain how I can solve these 2 problems?!

In early March, Phil Kalb bought shares of stocks in 2 different companies. Stock ABC rose 10% in value in March, then decreased 10% in April. Stock XYZ fell 10% in value in march, then rose 10% in April. What percent of its original price is each of these stocks now worth?

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A 5-pound weight is placed on a gymnasium scale. The scale dial displayed 5 1/2 pounds. If the scale is consistently off by the same percentage, how much does an athlete weigh, to the nearest tenth of a pound, if his weight displayed on this scale is 144 pounds?

Thanks So Much!

1. It might be easier if you look at specific stock prices. Suppose ABC was purchased at 100. It rose 10%, 10% of 100 is 10, so the new price is 110. Then it went down 10%, and 10% of 110 is 11, so the new price is 99.

XYZ went from 100, down to 90 then up to 99.

2. The true weight of any object is (weight shown) x (5 / 5.5).
The athlete weighs 144 x 5 / 5.5

You can take it from there.