Free powerpoint to teach the topics of Percentages to elementary school kids aspiring to compete in math contests such as the NLMC and Math Kangaroo

1. Percentages

2. Homework Review

3. Answer

4. Homework Review

5. Answer

6. Homework Review

7. Homework Review

8. Converting Units
Challenge Problem: How many seconds are in 1.5
weeks?
Try this problem on your own first. If you can't get the
answer, that’s ok. We’ll go over this problem once
everyone gives it a try.

9. Converting Units
Challenge Problem: How many seconds are in 1.5
weeks?

10. What is a Percentage?
●A percentage is the top part of a fraction whose
bottom part is 100
Examples:

11. What is a Percentage?
Percentages are very useful because they make it easy to
compare things
Example:

12. Finding the Percent
To solve _% of A is B
Change:
● the percentage to x
● of to multiplication
● is to =
Example: Find what percentage of 60 is 8.4?
Set up: x(60) = 8.4

13. Finding the Percent
Example: What percentage of 60 is 8.4?
Set up: x(60) = 8.4

14. Finding the Percent
Example: what percent of 68 is 34?

15. Finding the Percent
Answer: what percent of 20 is 23?
Now you try:
what percent of 60 is
50?

16. Finding the Percent
What we just did was basically changing a fraction to a
percent

17. Percentages
There are three parts in a percentage problem
1. The base is the whole part
2. The amount is part of the whole
3. The percent is the ratio of the amount to the base, written
as a percentage

18. Percentage Formulas

19. Percentage Formulas
Using these formulas:
Calculate the 20% of 300
The percent is 20%, the amount is 30, calculate the base

20. Percentage Formulas
Using these formulas:
The amount is 15, the base is 60,
what is the percentage?
Now you try: complete this table

21. Percentage Formulas
Answer:
33.3%
12
62.5

22. Percentage Word Problems
Example: The producer expected 500
people at the concert. 410 people
showed up. What percentage of the
expected attended the concert?

23. Percentage Word Problems
Example: The producer expected 500
people at the concert. 410 people
showed up. What percentage of the
expected attended the concert?
Asking for: the percent
Base: 500 people
Amount: 410 people
percent = 100(amount / base) = 100(410/500) = 82%

24. Percentage Word Problems
Example: There are 50 students in a
class. If 14% are absent on a particular
day, find the number of students
present in the class.

25. Percentage Word Problems
Example: There are 50 students in a
class. If 14% are absent on a particular
day, find the number of students
present in the class.
Asking for: the amount
Base: 50 students
Percentage: 14 percent
amount = (percent x base)/100 = (14 x 50)/100 = 7

26. Percentage Word Problems
Example: In an exam Ashley secured
332 marks. If she secured 83 %, find the
maximum marks.

27. Percentage Word Problems
Example: In an exam Ashley secured
332 marks. If she secured 83 %, find the
maximum marks.
Asking for: the base
Amount: 332 marks
percent: 83%
base = 100(amount / percent) = 100(332/83) = 400

28. Percentage Word Problems
Now you try: An alloy contains 26 % of
copper. What quantity of alloy is
required to get 260 g of copper?

29. Percentage Word Problems
Now you try: An alloy contains 26 % of
copper. What quantity of alloy is
required to get 260 g of copper?
Answer:
Asking for: the base
amount: 260 g copper
Percent: 26%
base = 100 (amount / percent) = 100 (260 /26) = 1000

30. NLMC Word Problems

31. Answer

32. Time for in-class practice!
Take out the in-class practice that you printed out at home and using
the concepts that we learned today, start working on them. If you
don’t finish that’s okay, you can finish it at home.