Class 8 - Mathematics
Comparing Quantities - Exercise 8.1
Top Block 1
Question: 1. Find the ratio of the following:
(a) Speed of a cycle 15 km per hour to the speed of scooter 30 km per hour.
(b) 50 m to 10 km
(c) 50 paise to Rs.5
(a) Speed of a cycle 15 km per hour to the speed of scooter 30 km per hour.
(b) 50 m to 10 km
(c) 50 paise to Rs.5
Answer :
Question: 2. Convert the following ratios to percentages:
(a) 3 : 4
(b) 2 : 3
(a) 3 : 4
(b) 2 : 3
Answer :
(a) Percentage of 3 : 4 = 3⁄4 x 100%
= 75%
(b) Percentage of 2 : 3 = 2⁄3 x 100%
= 662⁄3
(a) Percentage of 3 : 4 = 3⁄4 x 100%
= 75%
(b) Percentage of 2 : 3 = 2⁄3 x 100%
= 662⁄3
Question: 3. 72% of 25 students are good in mathematics. How many are not good in mathematics?
Answer :
Total number of students = 25
Number of good students in mathematics = 72% of 25 = 72⁄100 x 25 = 18
Number of students not good in mathematics = 25 – 18 = 7
Hence percentage of students not good in mathematics = 7⁄100 x 25 = 28%
Total number of students = 25
Number of good students in mathematics = 72% of 25 = 72⁄100 x 25 = 18
Number of students not good in mathematics = 25 – 18 = 7
Hence percentage of students not good in mathematics = 7⁄100 x 25 = 28%
Question: 4. A football team won 10 matches out of the total number of matches they played. If their win percentage was 40, then how many matches did they play in all?
Answer :
Let total number of matches be 𝓍.
According to question,
40% of total matches = 10
⇒ 40% of 𝓍 = 10
⇒ 40⁄100 x 𝓍 = 10
⇒ 𝓍 = (10 x 100)⁄40 = 25
Hence total number of matches are 25.
Let total number of matches be 𝓍.
According to question,
40% of total matches = 10
⇒ 40% of 𝓍 = 10
⇒ 40⁄100 x 𝓍 = 10
⇒ 𝓍 = (10 x 100)⁄40 = 25
Hence total number of matches are 25.
Question: 5. If Chameli had Rs. 600 left after spending 75% of her money, how much did she have in the beginning?
Answer :
Let her money in the beginning be Rs. 𝓍
According to question,
Let her money in the beginning be Rs. 𝓍
According to question,
Mddle block 1
Hence the money in the beginning was 荷2,400.
Question: 6. If 60% people in a city like cricket, 30% like football and the remaining like other games, then what percent of the people like other games? If the total number of people are 50 lakh, find the exact number who like each type of game.
Answer :
Number of people who like cricket
= 60%
Number of people who like football
= 30%
Number of people who like other games
= 100% – (60% + 30%) = 10%
Now Number of people who like cricket
= 60% of 50,00,000
= 60⁄100 x = 30,00,000
And Number of people who like football
= 30% of 50,00,000
= 30⁄100 x = 15,00,000
∴ Number of people who like other games = 10% of 50,00,000
= 10⁄100 x 50,00,000 = 5,00,000
Hence, number of people who like other games are 5 lakh.
Number of people who like cricket
= 60%
Number of people who like football
= 30%
Number of people who like other games
= 100% – (60% + 30%) = 10%
Now Number of people who like cricket
= 60% of 50,00,000
= 60⁄100 x = 30,00,000
And Number of people who like football
= 30% of 50,00,000
= 30⁄100 x = 15,00,000
∴ Number of people who like other games = 10% of 50,00,000
= 10⁄100 x 50,00,000 = 5,00,000
Hence, number of people who like other games are 5 lakh.