Comparing Quantities - Solutions
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 = = 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 = = 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 = = 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 = = 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 = computers
24 students needs = times 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 and area of U.P. = 2 lakh .
(i) How many people are there per km2 in both states?
(ii) Which state is less populated?
Answer: (i) People present per =
In Rajasthan = = 190 people per
In U.P. = = 830 people per
(ii) Rajasthan is less populated.