3) Maths Class 7 Chapter 8 Comparing Quantities- Ratios To Percent | Maths Class 7 CBSE By Deepak

3) Maths Class 7 Chapter 8 Comparing Quantities- Ratios To Percent | Maths Class 7 CBSE By Deepak

TOPICS TO BE STUDIED-
8.1 INTRODUCTION
8.2 EQUIVALENT RATIOS
8.3 PERCENTAGE – ANOTHER WAY OF COMPARING QUANTITIES
8.3.1 Meaning of Percentage
8.3.2 Converting Fractional Numbers to Percentage
8.3.3 Converting Decimals to Percentage
8.3.4 Converting Percentages to Fractions or Decimals
8.3.5 Fun with Estimation
8.4 USE OF PERCENTAGES
8.4.1 Interpreting Percentages
8.4.2 Converting Percentages to “How Many”
8.4.3 Ratios to Percents
8.4.4 Increase or Decrease as Per Cent
8.5 PRICES RELATED TO AN ITEM OR BUYING AND SELLING
8.5.1 Profit or Loss as a Percentage
8.6 CHARGE GIVEN ON BORROWED MONEY OR SIMPLE INTEREST
8.6.1 Interest for Multiple Years


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WHAT HAVE WE DISCUSSED?
1. We are often required to compare two quantities in our daily life. They may be heights, weights, salaries, marks etc.
2. While comparing heights of two persons with heights150 cm and 75 cm, we write it as the ratio 150 : 75 or 2 : 1.
3. Two ratios can be compared by converting them to like fractions. If the two fractions are equal, we say the two given ratios are equivalent.
4. If two ratios are equivalent then the four quantities are said to be in proportion. For example, the ratios 8 : 2 and 16 : 4 are equivalent therefore 8, 2, 16 and 4 are in proportion.
5. A way of comparing quantities is percentage. Percentages are numerators of fractions with denominator 100. Per cent means per hundred. For example 82% marks means 82 marks out of hundred.
6. Fractions can be converted to percentages and vice-versa.
7. Decimals too can be converted to percentages and vice-versa.
For example, 0.25 = 0.25 × 100% = = 25%
8. Percentages are widely used in our daily life,
(a) We have learnt to find exact number when a certain per cent of the total quantity is given.
(b) When parts of a quantity are given to us as ratios, we have seen how to convert them to percentages.
(c) The increase or decrease in a certain quantity can also be expressed as percentage.
(d) The profit or loss incurred in a certain transaction can be expressed in terms of percentages.
(e) While computing interest on an amount borrowed, the rate of interest is given in terms of per cents. For example, ` 800 borrowed for 3 years at 12% per annum

EXERCISE 8.1
1. Find the ratio of:
(a) ` 5 to 50 paise (b) 15 kg to 210 g
(c) 9 m to 27 cm (d) 30 days to 36 hours
2. In a computer lab, there are 3 computers for every 6 students. How many
computers will be needed for 24 students?
3. Population of Rajasthan = 570 lakhs and population of UP = 1660 lakhs.
Area of Rajasthan = 3 lakh km2
and area of UP = 2 lakh km2
.
(i) How many people are there per km2
in both these States?
(ii) Which State is less populated?