Page 39 - Start Up Mathematics_7

Example 20: Anny plants 5 saplings in a row in her garden. The distance between two adjacent
3
saplings is m. Find the distance between the first and the last sapling.
5
S1 S2 S3 S4 S5
Solution:

Let the saplings be planted at S1, S2, S3, S4 and S5.
3
Distance between two adjacent saplings = m
5
3 12 2
∴ Distance between S1 and S5 = 4 × = = 2 m
5 5 5
Example 21: A bike runs 64 km using 1 litre of petrol. How much distance will it cover using
1
3 litres of petrol?
4
Solution: Distance covered in 1 litre of petrol = 64 km
1 1 13
∴ Distance covered in 3 litres of petrol = 3 × 64 = × 64
4 4 4
= 13 × 16 = 208 km

8 16
Example 22: Write the fraction in the box, such that × = 100 . Reduce it in simplest form.
25
Solution: We know 8 × 2 = 16
∴ The numerator is 2.
Also, 25 × 4 = 100
∴ The denominator is 4.

Hence, the fraction in the box is 2 .
4
2 1
The simplest form of is .
4 2

2 3
Example 23: Out of a group of 160 students, opted for Science stream. of the Science students
5 4
chose to study Mathematics. How many Science students want to study Mathematics?

Solution: Total number of students = 160
2
Students opted for Science stream = × 160 = 64
5
3
Science students who want to study Mathematics = × 64 = 48
4
Thus, 48 Science students are interested in studying Mathematics.

EXERCISE 2.3

1. Multiply and reduce to the lowest form:
4 2 1 3 3 1 11 5
(a) and (b) 2 and 1 (c) 4 and 3 (d) and
5 7 4 4 4 2 3 6
2. Insert appropriate inequality sign, i.e., > or < in the given boxes.

3 6 1 15 1 20 1 3
(a) of of (b) of of
4 7 2 16 4 21 2 4

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