Proportion

Quantities will be in the same ratio! Direct Proportion Quantities will be in the same ratio! When 2 quantities are in direct proportion, if one increases the other increases. Also if one decreases, the other decreases.

1) 1 bottle of water costs 40c. Find the cost of 2 bottles. The Quantity and the Price are in DIRECT PROPORTION 2 bottles ? (more) 40 + 40 = 80 c or 40  2 = 80 c

2) 4 chocolates cost 80c. Find the cost of 3 chocolates. ? (less) 60 c How can you work it out?

4 chocolates cost 80c. Find the cost of 3 chocolates. 80  4 = 20 c 3 chocolates 20  3 = 60 c

3) We need 600 ml of water to make 3 glasses of orange squash 3) We need 600 ml of water to make 3 glasses of orange squash. How much water do we need to make 5 glasses ? 3 glasses 600 ml water 1 glass 600  3 = 200 ml 5 glasses 200  5 = 1000 ml Ans: 1000 ml = 1l

Time to practice! Find how much for ONE Then multiply by how many you need! This is called the unitary method!

3 packets of batteries cost €6. What is the cost of 5 packets? 3 packets  €6 1 packet  €6 ÷ 3 = €2 5 packets  5 x €2 = €10

5 bags of sweets contain 90 sweets 5 bags of sweets contain 90 sweets. Calculate how many sweets 7 bags will contain. 5 bags  90 sweets 1 bag  90 ÷ 5 = 18 7 bags 18 x 7 = 126 sweets

To make Tuna Stuffed Peppers for 8 people we need 200g tinned tuna To make Tuna Stuffed Peppers for 8 people we need 200g tinned tuna. How much do we need for 5 people 8 people 200g 1 person  200 ÷ 8 = 25g 5 people  25 x 5 = 125g

The cost of 6 cakes is €4.20. Find the cost of 5 cakes. 6 cakes  €4.20 1 cake  €4.20 ÷ 6 = 70c 5 cakes 70c x 5 = €3.50

3 packets of crisps weigh 84g. How much do 7 packets weigh? 3 packets  84g 1 packet  84g ÷ 3 = 28g 7 packets  28g x 7 = 196g

4 monkeys eat 16 bananas in 1 minute 4 monkeys eat 16 bananas in 1 minute. How many bananas do 13 monkeys eat in 1 minute? 4 monkeys  16 bananas 1 monkey 16 ÷ 4 = 4 bananas 13 monkeys 4 x 13 = 52 bananas