Assumption: This lesson is conducted to secondary 2 express class.

The pupils understand Algebra.

Scenario: Wanted to buy music CD by the

chinese pop group F-4. The CD costs $20. You check out stores for the best bargain……

10% discount +

20% discount

Further 10%

discount

on discounted price

Step 1:

Step 2:

Step 3:

Step 4:

$20 - $4 = $16 $20 - $2 = $18

$18 - $1.80 = $16.20

4$20100

20 2$20$

100

10

80.1$18100

10

Offers a better discount, and we buy the CD from there.

Step 1:

Step 2:

Step 3:

Step 4:

In General, for

Hence, Discount = 1 - (1 – d1/100) (1 – d2/100)

100d

1100d

1p

1001

1001d

1pd100d

1p

1001

100d

1pd100d

1p100d

100pd

p100d

21

21

12

12

11

100d

1p100pd

p 11

In short, we did this :

A) d1 / 100 , d2 /100

B) ( 1 – d1 / 100) , (1 – d2 / 100)

C) ( 1 – d1 / 100) x (1 – d2 / 100)

D) 1 - ( 1 – d1 / 100) x (1 – d2 / 100)

E) Covert answers in (4) into %

Use (-) for discount and (+) for increase.

Conclusion :We learn how to calculate the

actual discount/increases of successive discounts/increases.

QUESTIONS TO TRYWhen the price of a magazine was decreased by 15 % the sales increased by 20%. How were the receipts affected by these changes?Alice wants to buy a dress whose list price is $20. One store which generally discounts its dresses 12 % is offering an additional 20% on its already discounted price.A nearby store offers the same dress at a single 32% discount. Which store offers the lower price?