Pace Work 7-D 13/04

13/04
Тема: Відсотки в математиці

Хід уроку
 Today we are going to learn more about math percents and solve some problems.
                           
Presentation of new material
⦁ Percent (or per cent) means one hundredth.
⦁ The symbol for percent is  %.
Therefore, 1% means 1/100 or one hundredth,
 and 7% means 7/100 or seven hundredths.

⦁ The words “per cent” actually mean “per hundred” in Latin.         

Since percentages are just hundredth parts, we can very easily write them as fractions and as decimals.
63%  =   
63
100   =  0.63
⦁ A percent is just a fraction converted to be expressed as parts per hundred.
E.g.

Three quarters (3/4) is equivalent to (3x25) / (4x25) = 75/100 = 75%

0.123 = 12.3 / 100 = 12.3%

If you fill a 5 gallon container to 80% of its capacity it will contain 5 x 80% = 5 x (80/100) = 4 gallons.

If you score 45 correct answers out of a possible 90 questions your score, expressed as a percentage, is (45/90) x 100 = 50%

Percent is a proportional amount in relation to a whole, based on the whole amount being 100. For example, 50 percent of something is 50 of 100, which is equal to one half, and 75 percent equals 75 of 100, or three quarters.

100% of something means all of it.     1% of something means 1/100 of it.
⦁ To calculate a percentage of a quantity, we use the same method as when we calculate a fractional part of that quantity because percent simply means a hundredth part. Therefore, percentages are just fractions.
Now let’s read and study the tables (card#1).




T.: The first task for you is to write down the answers (card#1):

1) Write the fractions as percentages.

    a. About 4/5 ( _______ %) of the United States population is 14 years old or older.

    b. About 2/25 ( _______ %)  of the world’s population lives in North America.

    c. The continent of Africa covers about 1/5 ( _______ %) of the Earth’s total land mass.

2) Two trees are growing in Sandy’s front yard. The taller one is 5/4 as tall
    as the shorter one.

  a. Write the second sentence using a percent instead of a fraction.

  b. If the shorter tree is 160 cm tall, how tall is the taller tree?
3) Find 10% of these numbers.

a. 900   _______    b. 160   _______    c. 50   _______


2. Find 1% of these numbers.

a. 900  _______    b. 6,800  _______    c. 550  _______

4) If 1% of Cindy’s salary is $23, how much is her salary?

5) Ten percent of the cost of a pool is $430. How much does the pool cost?

Study the material and complete the tasks of the card#2

Thank you for your activities!
The lesson is over.