SUBJECT: Algebra
TOPIC: Linear Equations
LESSON: Solutions of word problems leading to linear
equations in one unknown
PREVIOUS KNOWLEDGE: Students can solve linear equations
TEACHING
AIDS: A chart with statements already translated to linear equations
LESSON OBJECTIVES: By the end of the lesson, students will
be able to translate and solve word problems leading to linear equations in one
unknown
TEACHING
METHODS: Demonstration, Question and
answer, Group discussion, and Assignment.
DURATION: 45 minutes
GRADE LEVEL:
7 ( Form 2)
INTRODUCTION:
When you add 3 to a number, your answer is 7. What is the
number? We can translate this statement
into a linear equation and solve as
below.
Solution
Let the number be x
Adding 3
gives; x+3
Answer is 7;
x+3=7(subtract 3 from both sides)
x+3-3=7-3
x+0=4
x=4
PRESENTATION:
We can use linear equations to solve word problems . To
solve any word problem using a linear equation, translate the word problem into
a linear equation . You can use any unknown of your choice. To double a number
means to multiply it by 2 and to treble a number means to multiply it by 3
Example 1:
Jane thinks of a number. She adds 5 to it. Her answer is 12. Find the number
Solution
Let the
number be x
She adds 5;
x+5
Her answer
is 12; x+5=12 (solve for x)
x+5-5=12-5
x+0=7
x=7 answer.
Example 2: I
think of a number. I subtract 6 from it and my result is 9. Find the number.
Solution
Let the
number y
I subtract
6; y-6
The result
is 9; y-6=9 (solve for y)
y-6+6=9+6
y-0=15
y=15 answer.
Example3: Jemia thinks of a number. He multiplies it by 3
and adds 6.the result is 18. Calculate the number.
Solution
Let the
number x.
He multiplies
it by 3; 3x.
Adds 6; 3x+6 .
Result is
18; 3x+6=18 (solve for x)
3x+6-6=18-6
3x+0=12
3x=12 (divide both sides by 3)
3x=12
3
3
x=4 answer
Example 4:
Eyong thinks of number. He divides it by 4 and subtracts 1.His answer is 9.
Find the number.
Solution
Let the number be k.
Divide by 4 ; k
4
Subtracts 1;
k -1
4
Result is
9; k -1=9 ( solve for K)
4
K
-1+1=9+1
4
K –0=10
4
K×4=10×4
4
k×1=40
k=40 answer
Example 5: A
boy has $500 more than another. Both have $1100 within them. How much does each
have?
Solution
Let b1 represent
first boy and b2 represent second boy.
Let b1
have $x and b2 have $(x+500).
Both have
$1100; $x+$(x+500)=$1100
Linear
Equation: x+x+500=1100
2x+500=1100
2x+500-500=1100-500
2x+0=600
2x=600
2x =600
2 2
x=300
b1=$300,
b2=$800
EVALUATION:
Solve the
following :
i)
Peter thinks of a number. He adds 6 to it. The result is 14,find the number.
ii)
Evelyn added
4 to a certain number. He multiplied by 5 and then added 8. If the final
result is 48, find the number.
CONCLUSION:
Assignment
iii)
I think of a number and double it.I divide the
result by 3. My answer is 8. Find the original number.
iv)
A father is 20 years older than his son. Find
the son’s age when he is 1 of his father’s age 5
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