Four Fundamental of Operation

Operations on Percent

By: Angel A. Abrilla Jr.Student Teacher

Rule #1

To multiply a number by any percent: convert the percent to its equivalent decimal number, then multiply it to the given.

Here are the examples

1.) 25% of 80 = 0.25 x 80=20

2.) 65% of 400 = 0.65 x 400=260

Rule #2To multiply by a fraction of 1%, first

get one percent of the number and multiply this product by the fraction of the percent given.

Here’s the example:

A. 1/3% of 300

means 1/3 of 1% of 300

1/3 of (1% of 300)

= 1/3 x 3 =1

Another example:

1\5% of 4500

means 1/5 of (1% of 4500)

1/5 of 45

=9

Rule #3

To multiply a number by any of these aliquot parts, it is easier to convert the percent first to the fractional equivalent then multiply.

Here’s the example:

A. 12 ½ % of P5600

=1/8 x P5600

= P700

Another example:

B. 83 1/3 % of P420

= 5/6 x P420

= P350

Rule #4

To divide a number by a percent, convert the percent to its decimal or fractional equivalent before doing the division

Here’s the given example:A. 18 is 36% of what number? Solution: 18/36% = 18/0.36 =1800/36 = 50

Another example:

48 is 37 ½ % of what number?

Solution:

48/37 ½%

= 48/ 3/8

= 48 x 8/3

= 128

48/37 ½%

= 48/ 37.5%

= 48/0.375

= 48000/375

= 128

Or

Answer the following given questions.1.) 50% of 5600

2.) 1% of 970

3.) What number of 50% is 2?

4.) What number of 10% is 15?

5.) 18 is what number of 25%

Answers:• 1.) ½ x 5600

• = 280

• 2.) 0.01 x 970

• = 9.7

• 3.) 2/.50 = 200/50

• = 4

• 4.) 15/.10 = 1500/10

• = 150

• 5.) 18/25% = 18/0.25 = 1800/25

• =72

How to multiply a number by any percent?

Convert the percent to its equivalent decimal number, then multiply.

How about multiplying a number by any of the aliquot parts? Convert the percent first to the fractional

equivalent then multiply.

If there are sales in the mall, is it good to buy a discounted item than the original price?

Find each number using a fraction for the percent.

• 1. 10% of 500

• 2. 20% of 60

• 3. 50% of 125

• 4. 50% of 540

• 5. 12 ½ % of 36

Answers:

• 1. 10/100 = 1/10 x 500 = 50

• 2. 20/100 = 1/5 x 60 = 12

• 3. 50/100 = ½ x 125 = 62/ ½ or 62.5

• 4. 50/100 = ½ x 540 = 270

• 5. 12.5/100 = 1/8 x 36 = 4/ ½ or 4.5

Get a piece of paper, find the total cost , including tax.

• 1. A hamburger meal costs P40. The sales tax is 4%.

• 2. A calculator sells for P850. The sales tax is 6%.

• 3. Jack bought 3 diskettes at P35 each, s 5% sales tax.

• 4. A record sells for P48. The sales tax is 7%.

Answers:

• 1.) Total cost: 38.4• Tax: 1.6

• 2.) Total cost: 799• Tax: 51

• 3.) Total cost: 105• Tax: 5.25

• 4.) Total cost: 44.64• Tax: 3.36

Assignment:Answer page 226, guided practice (B only) on Integrative Mathematics 6.