1. Calculating Percentages
Int 2
Simple Interest / Compound
Compound Interest
Appreciation / Depreciation
Inflation / Working back
Monday, April 10, 2017
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2. created by Mr. lafferty @ www.mathsrevision.com
Starter
Int 2
created by Mr.
Monday, April 10, 2017

3. Calculating Percentages
Int 2
Compound Interest
Appreciation
More
Simple Interest
Just Calculating Percentages
Inflation
Rising Prices
Depreciation
Less
Working
backwards
Monday, April 10, 2017
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4. Calculating Percentages
Int 2
Learning Intention
Success Criteria
To understand the
term simple interest and compound interest.
To know the meaning of the term simple interest.
To know the meaning of the term compound interest.
3. Know the difference between simple and compound interest.
Monday, April 10, 2017
created by Mr.

5. Calculating Percentages
Just working out percentages
Int 2
Simple Interest
I have £400 in the Bank. At the end of each year
I receive 7% of £400 in interest. How much interest
do I receive after 3 years. How much do I now have?
Monday, April 10, 2017
created by Mr.

6. Now try Exercise 1 Ch2 (page 8) Odd Numbers Calculating Percentages
Int 2
Now try Exercise 1
Ch2 (page 8)
Odd Numbers
Monday, April 10, 2017
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7. Calculating Percentages
Interest calculated on new value every year
Int 2
Compound Interest
Real life Interest is not a fixed quantity year after year. One year’s interest becomes part of the next year’s amount. Each year’s interest is calculated on the amount at the start of the year.
Principal value
Example
Daniel has £400 in the bank. He leaves it in the bank for 3 years. The interest is 7% each year. Calculate the simply interest and then the compound interest after 3 years.
Monday, April 10, 2017
created by Mr.

8. Calculating Percentages
Interest calculated on new value every year
Compound Interest
Int 2
Daniel has £400 in the bank. He leaves it in the bank for 3 years. The interest is 7% each year. Calculate the compound interest and the amount he has in the bank after 3 years.
Simple Interest
Y1 : Interest = 7% of £400 = £28
Amount = £400 + £28 = £428
Interest = 7% of £400 = £28
Y 2 : Interest = 7% of £428 = £29.96
3 x 28 = £84
Amount = £428 + £29.96 = £457.96
Y 3 : Interest = 7% of £ = £32.06
Amount = £ £32.06 = £490.02
Simple Interest is only £84
Compound is £ £400 = £90.02
Monday, April 10, 2017
created by Mr.

9. Now try Exercise 2 Ch2 (page 8 & 9) Calculating Percentages
Int 2
Now try Exercise 2
Ch2 (page 8 & 9)
Monday, April 10, 2017
created by Mr.

10. created by Mr. lafferty @ www.mathsrevision.com
Starter
Int 2
Monday, April 10, 2017
created by Mr.

11. Calculating Percentages
Int 2
Learning Intention
Success Criteria
To understand how to use the calculator to calculate compound interest easier.
To calculate compound interest using calculator..
Show appropriate working
when solving problems.
Monday, April 10, 2017
created by Mr.

12. Calculating Percentages
Int 2
This is called the multiplier.
Using a calculator to do Compound Formula
n = period of time
Days, months years
IMPORTANT
Can only use this when percentage is fixed
I = initial value
± = increase or decrease
V = Value
Monday, April 10, 2017
created by Mr.

13. Calculating Percentages
Int 2
Using a calculator to do Compound questions
Calculate the money in the bank after 3 years if the compound interest rate is 7% and the initial value is £400.
n = 3
I =400
± = increase =1.07
V= 400 x (1.07)3 = £490.02
Monday, April 10, 2017
created by Mr.

14. Calculating Percentages
Int 2
Using calculator to calculate Compound questions
In a jar bacteria grows 4% every hour. Initially there were 200 bacteria in the jar.
How many bacteria are in the jar 4 hours later.
n = 4
I =200
± = increase =1.04
V= 200 x (1.04)4 = 234
Monday, April 10, 2017
created by Mr.

15. Calculating Percentages
Int 2
Using calculator to calculate Compound questions
A car reduces in price by 14% each year. Initially it cost £
much is it worth 5 years later.
n = 5
I =12 500
± = increase =0.86
V= x (0.86)5 = £
Monday, April 10, 2017
created by Mr.

16. Calculating Percentages
Int 2
Now try
worksheet
Monday, April 10, 2017
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17. created by Mr. lafferty @ www.mathsrevision.com
Starter
Int 2
Monday, April 10, 2017
created by Mr.

18. Calculating Percentages
Int 2
Learning Intention
Success Criteria
To understand the terms appreciation and depreciation.
To know the terms appreciation and depreciation.
Show appropriate working
when solving problems containing appreciation and depreciation.
Monday, April 10, 2017
created by Mr.

19. Calculating Percentages
Int 2
Appreciation / Depreciation
Appreciation : Going up in value e.g. House value
Depreciation : Going down in value e.g. car value
Monday, April 10, 2017
created by Mr.

20. Average house price in Ayr has appreciated by 79% over past 10 years.
Quicker Method
Easier
1.79 x 64995
= £
Average house price in Ayr has appreciated by 79% over past 10 years.
If you bought the house for £64995 in 1994 how much would the house be worth now ?
Appreciation = 79% x £ 64995
= 0.79 x £64995
= £
New value = Old Value + Appreciation
= £ £
= £
Just working out percentages
Monday, April 10, 2017
created by Mr.

21. created by Mr. lafferty @ www.mathsrevision.com
Calculating Percentages
Int 2
A Mini Cooper cost £ in 2002
At the end 2003 it depreciated by 23%
At the end 2004 it will depreciate by a further 16%
What will the mini cooper worth at end 2004?
End 2003
Depreciation = 23% x £14625
= 0.23 x £14625
= £
New value = Old value - Depreciation
= £ £
= £
Monday, April 10, 2017
created by Mr.

22. created by Mr. lafferty @ www.mathsrevision.com
Calculating Percentages
Int 2
End 2003
Depreciation = 23% x £14625
= 0.23 x £14625
= £
New value = Old value - Depreciation
= £ £
= £
End 2004
Depreciation = 16% x £
= x £
= £
New Value = £ £
= £
Monday, April 10, 2017
created by Mr.

23. Calculating Percentages
Int 2
Now try MIA Ex 4
Ch2 (page 12)
Odd Numbers
Monday, April 10, 2017
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24. created by Mr. lafferty @ www.mathsrevision.com
Starter
Int 2
5cm
6cm
Monday, April 10, 2017
created by Mr.

25. Calculating Percentages
Int 2
Learning Intention
Success Criteria
Understand term inflation
and work out associated real-life problems.
Know the term inflation.
Work out real-life problems involving inflation.
Monday, April 10, 2017
created by Mr.

26. Calculating Percentages
Measure of how much prices rise each year.
Int 2
Inflation
Inflation is normally given in percentage form
and is normally in the range 0 – 10%
Example 1
In 2004 a worker received a wage of £300 per week.
If inflation is 2% in 2004, what should be his wage be in 2005.
2004 inflation = 2%
2% of £300 = £6
His wage should be £300 + £6 = £306
Monday, April 10, 2017
created by Mr.

27. Calculating Percentages
Measure of how much prices rise each year.
Int 2
Inflation
Inflation is normally given in percentage form
and is normally in the range 0 – 10%
Example 2
In 2002 a CD cost £8. The cost increases in line with inflation.
What is the price in 2003 if inflation is 1.5%.
2002 inflation = 1.5%
1.5% of £8 = £0.12
Price is £8 + £0.12 = £8.12
Monday, April 10, 2017
created by Mr.

28. Calculating Percentages
Int 2
Now try MIA Ex 6
Ch2 (page 15)
Monday, April 10, 2017
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29. Calculating Percentages
Int 2
Reversing the change
Example 1
After a 10% increase the price of a house is £
What was the price before the increase.
100 % % = £88 000
Deduce from question :
110 % = £88 000
We have :
1 % :
Price before is 100% :
£800 x 100 = £80 000
Monday, April 10, 2017
created by Mr.

30. Calculating Percentages
Int 2
Reversing the change
Example 2
The value of a car depreciated by 15%. It is now valued
at £2550. What was it’s original price.
100 % % = £2 550
Deduce from question :
85 % = £2 550
We have :
1 % :
Price before is 100% :
£30 x 100 = £3 000
Monday, April 10, 2017
created by Mr.

31. Calculating Percentages
Int 2
Now try MIA Ex 7
Ch2 (page 17)
Monday, April 10, 2017
created by Mr.