1. Direct Proportion

2. During break time, Syukri wishes to buy some sandwiches. No of sandwichTotal cost ($) 10.50 21.00 31.50 42.00 The total cost increases The no of sandwich increases The no of sandwich is directly proportional to the total cost The no of sandwich is directly proportional to the total cost Quantities that increase or decrease in the same ratio are said to be in direct proportion with each other. Direct proportion ???

3. Example 1 3 packets of sweets cost $12. How much will 10 packets cost? $12 ÷ 3 packets = $4.00 1 packet cost $4.00 Method 1 3 packets = $12 $4.00 x 10 packets = $40.00 Method 2 10 packets = y 3 x y = 10 x 12 3y = 120 y = 120/3 = $40

4. Example 2 A bus requires 20 litres of petrol to travel 280 km. Find the amount of petrol required for the bus to travel 70 km. 20 litres = 280 km Method 2 z = 70 km z x 280 = 20 x 70 280z = 1400 z = 1400/280 = 5 litres

5. Example 3 A cyclist travelled 7.5 km in 30 minutes. If he travels at a constant speed, find the distance he can travel if he cycles for hours. 7.5 km = ½ hours d = hours d x ½ = 7.5 x ½ d = 16.875 d = 16.875/ ½ = 33.75 km Convert minutes into hours. 30 min = ½ hr

6. Questions 1.What is the cost of 9 apples if 4 apples cost $1? 2.A cyclist travels 30 km in 1 hour. How far does he travel in 20 seconds?

7. Questions 1.5 apples cost $2.50, what would be the cost of 2 apples 2.7 cakes cost $5.60, what would be the cost of 10 cakes 3.9 plants cost $18.90, what would be the cost of 1 plant 4.8 cucumbers cost $4.32, what would be the cost of 3 cucumbers 5.6 t shirts cost $12.72, what would be the cost of 8 t shirts

8. Inverse Proportion

9. Azim asked a group of worker to paint his house. No of workersTime taken to complete the task (hour) 112 26 34 43 Time taken decreases The no of workers increases The no of workers is inverse proportional to the time taken The no of workers is inverse proportional to the time taken If one quantity decreases in the same ratio as another quantity increases, the two quantities are said to be in inverse proportion with each other. Inverse proportion ???

10. Example 1 A pack of rice for 20 men can last for 12 days. How long would the pack of rice last if there are 30 men? 20 men = 12 days Method 30 men = z z x 30 = 20 x 12 30z = 240 z = 240/30 = 8 days

11. Example 2 A car takes 75 minutes at 100 km/h to travel a stretch of road. Find the speed the car must travel if the journey takes 2 hours. 75 min = 100 km/h 120 min = y y x 120 = 75 x 100 120y = 7500 y = 7500/120 = 62.5 km/h Convert hour into minutes. 2 hr = 120 min

12. Questions 1.9 workers can build a wall in 10 days. How long would 6 workers take to build the same wall? 2.A cyclist takes half an hour to travel a stretch of road at a speed of 10 km/h. At what speed must he travel the same stretch of road if he is to take 20 minutes?

13. Direct/inverse proportion Determine whether each situation is a direct proportion or an inverse proportion problem. a) 3 workers can build an area of 12 m ² of the floor. How much area of the floor can 6 workers build? b) When 15 students share a sum of money, each student receives $16. If 20 students share the same sum of money, how much would each student receive?