NCERT Solution class 7 Mathematics EXERCISE- 8.2
CHAPTER – 8
EXERCISE – 8.2
Q1. Find the ratio of:
(a) Rs 5 to 50 paise
(b) 15 Kg to 210 g
(c) 9 m to 27 cm
(d) 30 days to 36 hours
SOLUTION:-
(a) We know that,
Rs 1 = 100 paise
Then,
Rs 5 = 5 x 100 = 500 paise
Now we have to find the ratio
= 500/5
= 10/1
So, the required ratio is 10:1.
(b) We know that,
1 kg = 1000g
Then,
15 kg = 15 x 1000 = 15000 g
Now we have to find the ratio,
= 15000/210
= 1500/21
= 500/7 [ divide both by 3]
So, the required ratio is 500:7.
(c) We know that,
1 m = 100 cm
Then,
9 m = 9 x 100 = 900 cm
Now we have to find the ratio
= 900/27
= 100/3 [ divide both by 9]
So, the required ratio is 100:3.
(d) We know that,
1 day = 24 hours
Then,
30 days = 30 x 24 = 720 hours
Now we have to find the ratio
= 720/36
= 20/1 [ divide both by 36 ]
So, the required ratio is 20:1.
Q2. In a computer lab, there are 3 computers for every 6 students. How many computers will be needed for 24 students?
SOLUTION:-
From the question it is given that,
Number of computer required for 6 students = 3
So, number of computer required for 1 student = (3/6)
= ½
So, number of computer required for 24 students = 24 x ½
= 24/2
= 12
Number of computer required for 24 students is 12 computers.
Q3. Population of rajisthan = 570 lakh and population of U.P = 1660 lakhs.
Area of rajisthan = 3 lakh km2and area of UP = 2 lakh km2.
(i) How many people are there per km2 in both these states?
(ii) Which state is less populated?
SOLUTION:-
(i) From the question , it is given that,
Population of rajisthan = 570 lakh
Area of rajisthan = 3 lakh km2
Then, population of rajisthan in 1 km2area = ( 570 lakh) / ( 3 lakh km2)
= 190 people per km2
Population of UP = 1660 lakh
Area of UP = 2 lakh km2
Then, population of UP in 1 lakh km2 area = (1660 lakh) / ( 2 lakh km2)
= 830 people per km2
(ii) By comparing in the two states rajisthan is less populated state.+++++++++
NCERT Solution for class 7 English Chapter 3