NCERT Solution class 7 Mathematics EXERCISE- 8.2

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.

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