DIGITAL TEXTBOOK

1. DIGITAL TEXT
BOOK
BASED ON THE TOPIC ‘RATIO’

2. RATIIO
Learning objectives:
 Understand the concept – ratio.
 solve problems based on ratio.
 use the concept ratio in an unfamiliar task.
Points to consider:
RATIO: A ratio is the relationship between two quantities
which expresses how many times one quantity is of the other
quantity of the same kind and in the same unit.
Remember:
The two quantities must be of the same kind and in the
same unit.
The ratio between two quantities is obtained by dividing
the first quantity by the second.
A ratio is a pure number and has no unit.
A ratio should always expressed in lowest terms.

3. EXAMPLE 1
Which ratio is greater 3:7 or 10:21 ?
Solution:
(By converting each ratio into a decimal fraction).
3:7=3/7=0.4285… and 10:21=10/21=0.4761…
As 0.4761… is greater than 0.4285…
EXAMPLE 2
Divide 832 rupees into two parts in the ratio 4:9.
Solution:
Since, 4+9=13
First part =4/13 of the whole=(4/13)*832=256
Second part=9/13 of the whole=(9/13)*832=576

4. EXAMPLE 3
Two numbers are in the ratio 5:4.If 3 is subtracted
from the first and 2 is subtracted from the second,
they become in the ratio 6:5.Find the numbers.
Solution:
Since, the numbers are in the ratio 5:4.
Let the numbers be 5x and 4x.
Given: (5x-3) ÷ (4x-2)=6 ÷5
25x-15=24x-12
25x-24x=15-12
X=3
Numbers are 15,12

5. TEST YOURSELF
1.Since, 2Kg=……..g
The ratio between 800g and 2kg=………=………=………
2.Can you express the ratio between 22 and 30
in lowest terms.
3.Which ratio is greater 5:7 or 11:24 ?
4.The ratio of the number of boys to the number
of girls in a school of 450 pupil is 4:5. Calculate
the number of girls and boys?
Answers
1.2000g, 2:5
2.11:15
3.5:7
4.200,250