Class 7 Maths Chapter 8 Comparing quantities Exercise 8.1 pdf notes:-
Exercise 8.1 Class 7 maths Chapter 8 Pdf Notes:-
Ncert Solution for Class 7 Maths Chapter 8 Comparing quantities Exercise 8.1 Tips:
In our daily life, there are many occasions when we compare two quantities.
Suppose we are comparing heights of Heena and Amir. We find thatHeena is two times taller than Amir.
Amir’s height is
1/2 of Heena’s height. Consider another example, where 20 marbles are divided between Rita and
Amit such that Rita has 12 marbles and
Amit has 8 marbles. We say,Rita has
3/2 times the marbles that Amit has.
2/3 part of what Rita has.Yet another example is where we compare speeds of a Cheetah and a Man. The speed of a Cheetah is 6 times the speed of a Man.Or The speed of a Man is 1/6 of the speed of the Cheetah.
Do you remember comparisons like this? In Class VI, we have learnt to make comparisons
by saying how many times one quantity is of the other. Here, we see that it can also be
inverted and written as what part one quantity is of the other.
In the given cases, we write the ratio of the heights as :
Heena’s height : Amir’s height is 150 : 75 or 2 : 1.
Can you now write the ratios for the other comparisons?
These are relative comparisons and could be same for two different situations.
If Heena’s height was 150 cm and Amir’s was 100 cm, then the ratio of their heights would be,
Heena’s height : Amir’s height = 150 : 100 = 150/100
3/2 = or 3 : 2.
This is same as the ratio for Rita’s to Amit’s share of marbles.
Thus, we see that the ratio for two different comparisons may be the same. Remember
that to compare two quantities, the units must be the same.
A ratio has no units.
Different ratios can also be compared with each other to know whether they are equivalent
or not. To do this, we need to write the ratios in the form of fractions and then compare
them by converting them to like fractions. If these like fractions are equal, we say the given
ratios are equivalent.
THINK, DISCUSS AND WRITE An ant can carry 50 times its weight. If a person can do the same, how much would you be able to carry?