Page 93 - Maths Skills - 7

Comparing Quantities 91

Percentage increase of ` 6 on ` 15 is 6 × 100 = 40%
15

 Increased value   6 
Or, we know that increase % =  ×100 =  × 100  = 40%

 Original value   15 
[ Q Increase = ` 6, and original value = ` 15]
\ Increase = 40%.

2
Example 6: In an orchard, 15 % of the trees are of mango. Find the number of other types of trees, if the total
3
number of trees in the orchard is 300.
Solution: Total number of all trees = 300

2 47 1
Number of mango trees = 15 % of 300 = × × 300 = 47
3 3 100
\ The number of other types of trees = 300 – 47 = 253.
Hence, the number of other types of trees in the orchard is 253.

Example 7: 25% of the teachers in a school are females and the number of male teachers is 51. Find the total
number of teachers in that school.
Solution: Let the total number of teachers be x. Alternative Approach
1
Percentage of female teachers = 25 25% is of 75%
3
Percentage of male teachers = (100 – 25) = 75 The number of male teachers is 51
1
Then, 75% of x = 51 \ of 51 is 17
3
or 75 × x = 51 which is the number of female teachers.
100 Therefore, the total number of teachers
or x = 51 × 100 = 68. (both male and female) = 51 + 17 = 68
75
Hence, the total number of teachers in the Hence, the total number of teachers in
school is 68. the school is 68.

Exercise 5.4

1. Amar obtained 420 marks out of 500 in CBSE XII class examination while his sister Sunita got 536
marks out of 600 in IX class examination. Find whose performance is better.

2. In a school there are 840 boys and 40% are girls. Find the number of girls.
3. A school is planning to increase the tuition fee by 15%. If the present monthly tuition fees is ` 350, find
the increased tuition fee.
4. The population of India is 100 crores. If its population increases by 2.5% every year, what will be its
population after 1 year?

5. In an examination, Amit obtained 65% marks. If the maximum marks are 500, find the marks obtained
by Amit.

6. Naveen travelled a distance of 15 km. He covered 75% of the distance by bus and the remaining distance
on foot. What distance did he travel by bus? How much distance did he cover on foot?