Ratio and Proportion:

Ratio: 

A comparison of two quantities by division is called a ratio.

A ratio can be written in different forms like a : b or a/b and is commonly read as, a is to b.

Proportion:

Equality of two ratios is called proportion.

A proportion is written as a : b : : c : d, and is read as a is to b as c is to d. Here, a/b = c/d where b & d are not equal to 0.

There are two types of proportions.

• Direct Proportion
• Inverse Proportion

Direct Proportion:

Direct proportion describes the direct relationship between two quantities. If one quantity increases, the other quantity also increases and vice-versa.

Inverse Proportion:

Inverse proportion describes the relationship between two quantities in which if one quantity increases, the other quantity decreases and vice-versa.

Practice Problems:

1. Write the below ratios in its simplest form.

     a)    3:9            b)    5 : 125            c)  2 : 16

2. The scale on the map is 1: 10000.What actual distance does a length

    of 5 cm on the map represent ?

3. In a school there are 850 pupils and 40 teachers. Write the ratio of 

    teachers to pupils.

4. If 15 liters of petrol cost BD 2.1. Find the cost of 50 liters of petrol.

5. If  3 copies of a book cost $ 27. Calculate the cost of 10 books.

6. Ali and Zahra are given BD 50. They decided to divide the money in

    the ratio 2:3. How much dose each receive ?

7. A train normally complete a 270 km journey in 4.5 hours. How much

   faster would it have to travel to complete the journey in 4 hours ?