Уроки математики и физики (RU + UA)

вторник, 20 декабря 2016 г.

Lesson 6. Percentages


Fractions and percentages.

Per cent means ‘out of 100’. Percentages are fractions with denominator (bottom number) equal to 100.

EXAMPLES:

63% means 63/100
7% means 7/100.

17 out of 100 small squares are shaded.
Fraction shaded = 17/100
Percentage shaded = 17%.

Changing percentages into fractions.

EXAMPLES:


41% = 41/100
Changing fractions into percentages.

EXAMPLES:
To change a fraction into a percentage, multiply the fraction by 100.
(to the nearest whole number)

Percentage of a number.

Common percentages.

50% = 1/2    25% = 1/4    75% = 3/4    
331/3% = 1/3    662/3% = 2/3

EXAMPLES:

25% of 60 = 1/4 × 60 = 60 ÷ 4 = 15.
75% of 36 = 3/4 × 36 = (36 ÷ 4) × 3 = 27.
662/3% of 24 = 2/3 × 24 = (24 ÷ 3) × 2 = 16.

Multiples of 10%

10% = 1/10

To work out 20%, find 10% then multiply by 2.
To work out 30%, find 10% then multiply by 3 and so on.

Harder percentage.
To find 1% of a number, divide the number by 100.

EXAMPLES:

Find 23% of a number. Divide the number by 100 to find 1% then multiply by 23 to find 23% of the number.
Find 12% of 2300

1% of 2300 = 2300 ÷ 100
12% of 2300
= (2300 ÷ 100) × 12 = 276

Percentages and decimals.

EXAMPLES:
NOTE
To change decimals into percentages, the first two numbers after the point give the percent:
NOTE

Tasks to the lesson 6

Other lessons:

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