Forming Simple Equations (1)

Forming simple equations involving addition and subtraction

Group Activity 1

In groups of four:

Put 4 bottle tops on one side of a beam balance.
Put 10 bottle tops on the other side of the beam balance.
Add one bottle top at a time on the side with 4 bottle tops. Continue adding the bottle tops until the two sides of the beam are balanced.
Discuss and share with other groups.

Note

The number of bottle tops added can be represented by a letter x. The activity can be as shown:

x + 4 = 10

The statement, x + 4 = 10 is an equation.

Example 1. Subtraction

Soi is 20 years old. Njau is 5 years older than Soi. If Njau is x years old, write an equation to represent the information.

Njau is x years old.
Soi is x – 5 years old.
So, the equation is

x – 5 = 20

Example 2. Addition

John had some guava fruits in his bag. Maria gave him 3 more guava fruits. He had 7 guava fruits altogether. Form an equation to show this information:

Let John have x guava fruits. Then

x + 3 = 7

Exercise A

Ndunda bought x mangoes. He ate 3 of the mangoes. He was left with 11 mangoes. Form an equation to represent this information.

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Nafula had Sh x in her bag. Khahi had Sh 30. They had a total of Sh 70. Write an equation to represent the information.

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There were y eggs in a basket. Kimuli used 4 eggs to make a cake. There were 8 eggs remaining in the basket. Form an equation to show this information.

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Serah had some money (m) in her bag. Her mother gave her Sh 100. She had Sh 350 altogether. Write an equation to represent this information.

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Mukundi had c goats. Kahua had 8 goats. They had 40 goats altogether. Form an equation on the total number of goats.

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There was some water (w) in a drum. Waiku used 25 litres of the water. There were 50 litres remaining in the drum. Write an equation to represent this information.

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There were m people in a security meeting. Five more people came in for the meeting. There were 105 people altogether. Form an equation to show this information.

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