Calculating Simple Percentages

What is 80% of 80?

Calculating Simple Percentages

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What is a percentage? A percentage is a way in which you can express a fraction (or a part of a whole) in portions of 100. In word form, a percentage would look like this:

Part/Whole = Percent/100

The symbol used to show percent is “%” so 17 percent would be 17%. The “17” is the “part” and the “%” is the whole which means that 17% can also be shown as 17/100.

How to Find the Percentage of Any Given Number:

In math you will often have to find the percentage of a number. For example, if you were to go shopping and you found a new shirt that was 20% off, you would need to know what is the number the 20% is off of. The sales tag on the shirt says $20.00. So now you would need to know how to find what 20% of $20.00 is. To do this you must multiply the number ($20.00) by the percent “20”. However if you multiply 20.00 x 20, you would get the answer: “400.00”. That would not be correct. Why, because we need to multiply $20.00 by 20%, not by “20”.

20% must be converted to a decimal number. We know that 20% also equals 20/100. The “100” (which replaces the % symbol) needs to be used to create a decimal number. To show 20/100 as a decimal, we must move a decimal point over to the left, beginning to the immediate right of the “0” in “20”, two spaces so 20/100 becomes .20. That decimal point is used in place of the “100” and/or the “%”. We can then multiply $20.00 by .20 so: 20.00 x .20 = 4.00. This tells us that 20% of $20.00 is $4.00.

How to Determine the Percentage of Any Given Number:

Now if you are looking to find what the percentage is, let’s say if you took 20 cans of soda from a package of 80, you would need to divide 20 by 80 so it would be written out as: 20 ÷ 80 = .25. Now we must reverse the decimal to a percentage. To do this, we now need to move the decimal point over two spaces to the right so that .25 becomes 25 and the decimal becomes the symbol “%” so the answer would be 25%. This means that 20 cans of soda removed from a package of 80 cans equals 25%.

1.
20% of 350
140
70
60
55
20% converts to 20/100 or in decimal form, .20. We can eliminate the “0” after the .2 and simply use .2 to find our answer. We then multiply 350 by .2 or 350 x .2 = 70. Answer (b) is the correct answer
2.
30% of 150
45
48
51
53
30% converts to 30/100 or in decimal form, .30. We can eliminate the “0” after the .3 and simply use .3 to find our answer. We then multiply 150 by .3 or 150 x .3 = 45. Answer (a) is the correct answer
3.
70% of 200
120
140
160
170
70% converts to 70/100 or in decimal form, .70. We can eliminate the “0” after the .7 and simply use .7 to find our answer. We then multiply 200 by .7 or 200 x .7 = 140. Answer (b) is the correct answer
4.
90% of 140
126
130
120
110
90% converts to 90/100 or in decimal form, .90. We can eliminate the “0” after the .9 and simply use .9 to find our answer. We then multiply 140 by .9 or 140 x .9 = 126. Answer (a) is the correct answer
5.
50% of 170
85
135
45
90
50% converts to 50/100 or in decimal form, .50. We can eliminate the “0” after the .5 and simply use .5 to find our answer. We then multiply 170 by .5 or 170 x .5 = 85. Answer (a) is the correct answer
6.
80% of 70
50
54
56
58
80% converts to 80/100 or in decimal form, .80. We can eliminate the “0” after the .8 and simply use .8 to find our answer. We then multiply 70 by .8 or 70 x .8 = 56. Answer (c) is the correct answer
7.
40% of 110
60
55
44
35
40% converts to 40/100 or in decimal form, .40. We can eliminate the “0” after the .4 and simply use .4 to find our answer. We then multiply 110 by .4 or 110 x .4 = 44. Answer (c) is the correct answer
8.
80% of 80
48
58
62
64
80% converts to 80/100 or in decimal form, .80. We can eliminate the “0” after the .8 and simply use .8 to find our answer. We then multiply 80 by .8 or 80 x .8 = 64. Answer (d) is the correct answer
9.
10% of 45
45
4.05
4.5
4
10% converts to 10/100 or in decimal form, .10. We can eliminate the “0” after the .1 and simply use .1 to find our answer. We then multiply 45 by .1 or 45 x .1 = 4.5. Answer (c) is the correct answer
10.
60% of 20
6
8
9
12
60% converts to 60/100 or in decimal form, .60. We can eliminate the “0” after the .6 and simply use .6 to find our answer. We then multiply 20 by .6 or 20 x .6 = 12. Answer (d) is the correct answer
Author:  Christine G. Broome

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