1. Rachel went to the supermarket.
She bought some fruit
for herself and for her neighbour.
A powerpoint presentation by
Winston Micallef
Head of Department (Mathematics)
However,
she forgot to ask
for separate bills!

2. the price labels on the fruit, she could not read them!
When Rachel checked
the price labels on the fruit,
she could not read them!
- = - _= cents
- = - _= cents

3. She knew that she had bought 5 apples and 5 bananas for 90 cents
WW Supermarket
5 apples
5 bananas
TOTAL Lm0.90
but needed to know the price of each
so that she could charge her neighbour accordingly.

4. Luckily, Rachel found yesterday’s bill.
WW Supermarket
5 apples
3 bananas
TOTAL Lm0.70
She was charged
70 cents for 5 apples and 3 bananas.

5. Rachel considered herself lucky
because she realised that she now knew how to work out
the price of an apple and a banana!

6. Do ?
you

7. Today’s bill Yesterday’s bill
WW Supermarket
5 apples
3 bananas
TOTAL Lm0.70
Yesterday’s
bill
WW Supermarket
5 apples
5 bananas
TOTAL Lm0.90

8. cents on each apple price label.
This is what Rachel did. a
She wrote
cents on each apple price label.

9. b
and
cents on each banana
price label.

10. 5 (a cents) 5(b cents) + = 90 cents a cents a cents b cents b cents

11. Similarly, yesterday’s bill would be…
5 (a cents) +
5(b cents)
= 90 cents
Similarly, yesterday’s bill would be…
5 (a cents) + 3(b cents) = 70 cents
5 a + 5 b = 90
5 a + 3 b = 70
In short…

12. 5 a + 5 b = 90
5 a + 3 b = 70

13. Can you now guess what she did?

14. She subtracted the bills!!
5 a + 5 b = 90
5 a + 3 b = 70
2 b = 20
b = 10
b cents is 10 cents

15. a = 8 a cents is 8 cents b cents is 10 cents, As… 5 a + 5 b = 90 then…

16. Now Rachel can charge her neighbour because she found out that
an apple costs 8 cents
and a banana costs 10 cents!

17. I want to see the solutions again...
I want to see the whole story again…