I'll do the first four problems to get you started
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Problem 15
<h3>Answer: 40%</h3>
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Explanation:
The price dropped by $60, since 150-90 = 60. This is the discount, which is the amount you save. Divide this over the original price ($150) and we get 60/150 = 0.40 = 40%
Therefore, the price has been reduced by 40%. If we take 40% of 150, then 0.40*150 = 60 showing that 40% of $150 is 60 dollars. This matches up with the discount value mentioned earlier. So it helps verify the answer.
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Problem 16
<h3>Answer: 20%</h3>
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Explanation:
The pay raised by 12-10 = 2 dollars. So the percent increase is 2/10 = 0.20 = 20%
Note how 20% of 10 = 0.20*10 = 2 is the pay raise amount; meaning that 2 is 20% of 10.
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Problem 17
<h3>Answer: 50%</h3>
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Explanation:
I'll use a formula this time, but we could follow the same idea as the previous problems. This is to give another approach.
A = old value = 8
B = new value = 12
C = percent change
C = [ (B-A)/A ] * 100%
C = [ (12-8)/8 ] * 100%
C = (4/8)*100%
C = 0.50*100%
C = 50%
50% is the same as half of the value. Note how half of 8 is 4, ie 50% of 8 = 0.50*8 = 4. So this is the amount of increase when going from 8 to 12.
Side note: The "B-A" portion in the numerator represents the change in value. We divide this change over the original amount "A" and then multiply by 100% to get the percent change we're after.
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Problem 18
<h3>Answer: 24%</h3>
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Explanation:
I'll use the formula again
A = old value = 3.00
B = new value = 2.28
C = percent change
C = [ (B-A)/A ] * 100%
C = [ (2.28-3.00)/3.00 ] * 100%
C = (-0.72/3.00)*100%
C = -0.24*100
C = -24%
The negative percent change means we have a percent decrease. So we have a 24% decrease. Since your teacher is asking about how much the percent reduction is, we'll write the positive version of this percentage.
Problems 19 through 22 will follow the same ideas as shown in the previous problems.
