Comparing Quantities - Solutions 1

CBSE Class –VII Mathematics
NCERT Solutions
Chapter 8 Comparing Quantities (Ex. 8.1)

Question 1. 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
Answer: To find ratios, both quantities should be in same unit.
(a) Rs. 5 to 50 paise
 5 x 100 paise to 50 paise            [Rs. 1 = 100 paise]
 500 paise to 50 paise
Thus, the ratio is = 50050=101 = 10 : 1
(b) 15 kg to 210 g
 15 x 1000 g to 210 g                   [  1 kg = 1000 g]
 15000 g to 210 g
Thus, the ratio is = 15000210=5007 = 500 : 7
(c) 9 m to 27 cm
 9 x 100 cm to 27 cm                   [  1 m = 100 cm]
 900 cm to 27 cm
Thus, the ratio is = 90027=1003 = 100 :3
(d) 30 days to 36 hours
 30 x 24 hours to 36 hours           [  1 day = 24 hours]
 720 hours to 36 hours
Thus, the ratio is = 72036=201 = 20 : 1
Question 2. In a computer lab, there are 3 computers for every 6 students. How many computers will be needed for 24 students?
Answer: 6 students needed = 3 computers
Therefore 1 student needs = 36 computers
24 students needs = 36times 24 = 12 computers
Thus, 12 computers will be needed for 24 students.
Question 3. Population of Rajasthan = 570 lakhs and population of U.P. = 1660 lakhs. Area of Rajasthan = 3 lakh km2and area of U.P. = 2 lakh km2.
(i) How many people are there per km2 in both states?
(ii) Which state is less populated?
Answer: (i) People present per km2PopulationArea
In Rajasthan = 570 lakhs3 lakhs km2 = 190 people per km2
In U.P. = 1660 lakhs2 lakh km2 = 830 people per km2
(ii) Rajasthan is less populated.