Topicmf3c8379dbacb6a0e_1528449000663_0Topic

Calculating a number based on its percent

Levelmf3c8379dbacb6a0e_1528449084556_0Level

Second

Core curriculummf3c8379dbacb6a0e_1528449076687_0Core curriculum

V. Percentage calculations. The student:

4) calculates number b whose p percent is equal to a.

Timingmf3c8379dbacb6a0e_1528449068082_0Timing

45 minutes

General objectivemf3c8379dbacb6a0e_1528449523725_0General objective

Doing simple calculations mentally or using the long method in more difficult examples, using these abilities in practical situations.

Specific objectivesmf3c8379dbacb6a0e_1528449552113_0Specific objectives

1. Doing simple calculations mentally or using the long method in more difficult examples, using these abilities in practical situations.

2. Applying calculating percentage calculations to do text exercises.

3. Communicating in English, developing basic mathematical, computer and scientific competences, developing learning skills.

Learning outcomesmf3c8379dbacb6a0e_1528450430307_0Learning outcomes

The student:

- calculates a number based on its percent,

- applies calculating percentage calculations to do text exercises.

Methodsmf3c8379dbacb6a0e_1528449534267_0Methods

1. Situational analysis.

2. JIGSAW.

Forms of workmf3c8379dbacb6a0e_1528449514617_0Forms of work

1. Work in pairs.

2. Group work

Lesson stages

Introductionmf3c8379dbacb6a0e_1528450127855_0Introduction

On the board there are puzzles: “Guess what number this is?”
- 50 % of this number is equal to 30.
- 25% of this number is equal to 30.
- 10% of this number is equal to 30.
Students’ task is to find this number and ways to calculate it.

Conclusions students should draw

To find the searched number we need to:
- multiply times 2, if we have 50% of the number;
- multiply times 4, if we have 25% of the number;
- multiply times 10, if we have 10% of the number.mf3c8379dbacb6a0e_1527752263647_0To find the searched number we need to:
- multiply times 2, if we have 50% of the number;
- multiply times 4, if we have 25% of the number;
- multiply times 10, if we have 10% of the number.

The teacher introduces the subject of the lesson – calculating a number based on any its percent.

Proceduremf3c8379dbacb6a0e_1528446435040_0Procedure

Students work individually, using computers. Their task is to get to know the INTERACTIVE ILLUSTRATION, that shows one of the method of calculating a number based on its percent.

[INTERACTIVE ILLUSTRATION]

After having completed the exercise, they present results of their observations:
To find a number based on its percent we need to:
1. calculate how much is 1% of the searched number;
2. calculate how much is 100% of the searched number.
Students do exercises using learnt method.

Task
Find the number whose:
a) 30% is 150,
b) 450% is 6000,
c) 45% is 900,
d) 240% is 192.

The teacher informs students that we can also identify a number based on its percent, using proper equations.
Students work using the JIGSAW method.
The teacher divides students into 3 persons groups. Each member of the group gets different task from the tasks below. After solving the tasks, students gather in groups that were doing the same task. They discuss the solutions and clarify any doubts. Then, they return to the initial groups and present the solutions to other members.

Task
Do the exercise using the formula.

Formula:
Find the number whose 12% is 42.

We marked
x – searched number

[Illustration 1]

Task
Find the number whose:
a) 60% is 180,
b) 220% is 462,
c) $14\frac{2}{7}$% is $6\frac{3}{4}$.

Task
Do the exercise using the formula.

Formula:
A TV costs 4930 PLN after 15% discount. How much did the TV cost before the discount?

[Illustration 2]

Task
After lowering the price of a jacket by 10%, it cost 630 PLN. How much did it cost before lowering the price?

Task
Do the exercise using the formula.

Formula:
An avocado costs 4,34 after 24% raise of the price.
How much did it cost before the raise?

[Illustration 3]

Task
After raising prices of tram tickets by 10%, Miss Kasia had to pay 3,85 PLN. How much did this ticket costs before the raise?

The teacher evaluates the students’ work and clarifies doubts.

An extra task
Karol got 1350 PLN of a bonus, that is 30% of his salary. How much does he make a month?

Lesson summarymf3c8379dbacb6a0e_1528450119332_0Lesson summary

Students do the revision exercises. Then together they sum‑up the classes, by formulating the conclusions to memorise.
To find the searched number we need to:
- multiply times 2, if we have 50% of the number;
- multiply times 4, if we have 25% of the number;
- multiply times 10, if we have 10% of the number.
- calculate how much is 1% of the searched number and multiply it times 100,
- solve a proper equation.

Selected words and expressions used in the lesson plan

calculating how much is 1% of the given numbercalculating how much is 1% of the given numbercalculating how much is 1% of the given number

finding a number when we have a percent givencalculating how much is 1% of the given numberfinding a number when we have a percent given

finding a number when we have 50% of this numberfinding a number when we have 50% of this numberfinding a number when we have 50% of this number

finding a number when we have 25% of this numberfinding a number when we have 25% of this numberfinding a number when we have 25% of this number

finding a number when we have 10% of this numberfinding a number when we have 10% of this numberfinding a number when we have 10% of this number

solving appropriate equationsolving appropriate equationsolving appropriate equation