2.5 application of percents. key words: –“of” means “multiply” –“is” means “= ”...
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2.5 Application of Percents
• Key words:– “of” means “multiply”– “is” means “= ”– “what number?”
means “x”
• To convert a decimal number to %, move the decimal 2 places to the right– Ex: 0.51 = 51%
• To convert from % to decimal number, move the decimal 2 places to the left
- Ex: 6% = 0.06
• Formula:
100
%
of
is
1) 13% of 80 is what number?
0.13 * 80 = x
x = 10.4
So 13% of 80 is 10.4
So 13% of 80 is 10.4
of
is
100
%
80100
13 x
1040100 x
4.101001040 x
2) What number is 60% of 70?
So 42 is 60% of 70
of
is
100
%
70100
60 x
4200100 x1004200x
42x
3) 43 is 20% of what number?
• So 43 is 20% of 215
of
is
100
%
x
43
100
20
430020 x215204300 x
4) 110% of what number is 30?
• So 110% of 27.27 is 30
of
is
100
%
x
30
100
110
3000110 x27.271103000 x
5) 16 is what percent of 80?
So 16 is 20% of 80
of
is
100
%
80
16
100
x
160080 x20801600 x
6) What percent of 94 is 10.5?
So 11% of 94 is 10.5
of
is
100
%
94
5.10
100
x
105094 x11941050 x
7) A camera is on sale for $250. That was 40% of the original price. What was the original price?
So the original price is $625
of
is
100
%
x
250
100
40
2500040 x6254025000 x
8) A player completed 42.9% of his field goals. He made 283 field goals. How many did he attempt?
So he attempted 660 field goals.
x
283
100
9.42
283009.42 x
of
is
100
%
7.6599.4228300 x
9) Jerry left a $7.92 tip on a meal that costs $36. What percent of the meal’s cost was the tip? Find the total cost including the tip?
So he paid 22% tip.
The total cost is: 36 + 7.92 = $43.92
of
is
100
%
79236 x36
92.7
100
x
2236792 x
10) Peter left a 18% tip on a meal. Including the tip, its cost was $35.40. What was the cost of the meal before the tip?
Meal’s cost + tip = total cost
x + 0.18x = 35.40
1.18x = 35.4
x = 30
So the cost of the meal before tip
is $30.
We should not use this formula because the total cost is more than 100% (it should be 118%). So we need to modify the formula
of
is
100
%
40.35118
100 x
30
3540118
x
x
11) A person’s income is $18,500 per year. Federal tax is 15% of that income. How much would that person pay for Federal income tax?
So she pays $2775 for tax
of
is
100
%
18500100
15 x
2775
277500100
x
x
12) A purchase of $44 has a sales tax of $2.31. What is the sales tax rate (or percent)?
The sale tax rate is 5.25%
of
is
100
%
44
31.2
100
x
25.5
23144
x
x
13) A pair of jeans that regularly costs $26 is on sale at 40% off. What is the sale price?
• So the sale price is $15.60
of
is
100
%
26100
60 x
6.15
1560100
x
x
14) Mary’s salary is $25,000 per year. She just gets a 26% raise. Find her new salary?