**TOPIC 9: RATIO, PROFIT AND LOSS ~ MATHEMATICS FORM 1**

Ratio

A ratio – is a way of comparing quantities measured in the same units

Examples of ratios

A class has 45 girls and 40 boys. The ratio of number of boys to the number of girls = 40: 45

A football ground 100 𝑚 long and 50 𝑚 wide. The ratio of length to the width = 100: 50

**NOTE:**Ratios can be simplified like fractions

- 40: 45 = 8: 9
- 100: 50 = 2: 1

A Ratio in its Simplest Form

Express a ratio in its simplest form

Example 1

Simplify the following ratios, giving answers as whole numbers

Solution

A Given Quantity into Proportional Parts

Divide a given quantity into proportional parts

Example 2

Express the following ratios in the form of

**Solution**

To increase or decrease a certain quantity in a given ratio, multiply the quantity with that ratio

Example 3

- Increase 6 𝑚 in the ratio 4 ∶ 3
- Decrease 800 /− in the ratio 4 ∶ 5

Solution

**Simple Interest**

Simple Interest

Calculate simple interest

The amount of money charged when a person borrows money e. g from a bank is called interest (I)

The amount of money borrowed is called principle (P)

To calculate interest, we use interest rate (R) given as a percentage and is usually taken per year or per annum (p.a)

Real Life Problems Related to Simple Interest

Solve real life problems related to simple interest

Example 7

Mrs.

Mihambo deposited money in CRDB bank for 3 years and 4 months. A t the

end of this time she earned a simple interest of 87, 750/− at 4.5% per

annum. How much had she deposited in the bank?

Mihambo deposited money in CRDB bank for 3 years and 4 months. A t the

end of this time she earned a simple interest of 87, 750/− at 4.5% per

annum. How much had she deposited in the bank?

**Solution**

Given I = 87, 750/− R = 4.5% % T = 3 years and 4 months