Ncert Solutions For Class 7 Maths Ex 8.1

Ncert Solutions For Class 7 Maths Chapter 8 Ex 8.1

QUESTION 1:

Calculate the ratio:

            (i) Rs10 to 50 paise                      (ii) 10kg to 500g

           (iii) 60m to 20cm                          (iv) 20days to 50 hours

Solution;

(i) Rs.10 to 50 paise

=> 10 x 100 = 1000 paise            (Since , Rs.1 = 100 paise)

Thus, the ratio =  1000/50 = 20 : 1

(ii) 10kg to 500g

10 x 1000= 10000g (Since 1kg is 1000g)

Thus, the ratio = 10000/500 = 20 : 1

(iii) 60m to 20cm

60 x 100 = 6000cm (Since 1m = 100cm)

Thus, the ratio =6000/20 = 300 : 1

(iv) 20days to 50 hours

20 x 24 = 480 hours

Thus, the ratio = 480/50 = 48 : 5

 

QUESTION 2:

A computer lab has 2 computers for every 4 students. For 20 students how many computers will be required?

Solution;

Given,

4 students = 2 computers

1 student requires = 2/4 computers.

Therefore, 20 students require = (2/4) x 20 = 10 computers.

 

QUESTION 3:

Mizoram has a population of 10 lakh and Sikkim has a population of 6 lakh. Area of Mizoram is  21,000 km2 and the area of Sikkim is 7000 km2.

            (i) Find the number of people per km2 in both the states.

            (ii) Which state has a lesser population?

Solution;

(i) People per km2 = Population/ Area

In Mizoram = 1000000/21000 = 47.61 ≃48 people/km2

In Sikkim      = 600000/7000         = 85.71 ≃ 86 people/km2

(ii) Sikkim has a lesser population.