Questions on Percentages

1
Questions on Percentages

• Most percentages type questions take the form
• initial value x percentage change final value

2
Type 1 Finding the final value

• Example What is the new price of a car costing
  7,500 after a 6 price increase?
  Have a go at
  answering this question
• Now look to see if you were correct. There are
  two methods you could use

3
Type 1 Finding the final value

• Example What is the new price of a car costing
  7,500 after a 6 price increase
• Method 1
• Initial price x increase 7500x 6
• 7500
  x 6/100
• 450
• Final Price original increase
• 7500 450
• 7950

4
Type 1 Finding the final value

• Example What is the new price of a car costing
  7,500 after a 6 price increase
• Method 2
• Initial price x increase final price
• 7500 x 106
• 7500 x 106
• 100
• 7500 x 1.06 7950
• Were you correct? Now try another similar example
  

5
Type 1 Finding the final value decrease

• In a sale a leather jacket costing 150 was
  reduced by 15. What was the sale price?
• Check that you can do this with and without a
  calculator.

6
Type 1 Finding the final value decrease

• In a sale a leather jacket costing 150 was
  reduced by 15. What was the sale price?
• Method 1
• Initial price x decrease 150x 15
• 150 x
  15/100
• 22.50
• Final Price original - decrease
• 150 - 22.50
• 127.50

7
Type 1 Finding the final value decrease

• In a sale a leather jacket costing 150 was
  reduced by 15. What was the sale price?
• Method 2
• Initial price x increase final price
• 150 x 85
• 150 x 85/100
• 150 x 0.85 127.50
• Were you correct?

8
Percentages - Type 1

• Have a go at practising some questions

9
Type 2Finding the changeYou know the initial
value and the final value

• The price of a house goes up from 160,000 to
  175,000. Find the increase
• Have a go at doing this question

10
Type2Finding the changeYou know the initial
value and the final value

• The price of a house goes up from 160,000 to
  175,000. Find the increase
• change difference x 100
• initial price
• 175000 - 160000 x 100
• 160000
• 9.4

11
Type2Finding the changeYou know the initial
value and the final value

• Now practise some questions like this

12
Type 3 Finding the initial value before any
change

• A discman is reduced in a sale by 25 to 60 What
  was the initial value?

These questions are often badly done
If the cost has been reduced by 25, then the 60
represents 75 of the initial cost 75 60
1 60/75 100 60/75 x 100 80
13
Type 3 Finding the initial value before any
change

• Again practise some examples

14
Questions on Percentages

• Most percentages type questions take the form
• initial value x percentage changefinal value

Decide what type of question you have before you
start