Grade C Problems with Compound Units Solve problems
Grade C Problems with Compound Units Solve problems involving compound units such as speed, rates of pay, unit pricing, density and pressure.
Key Vocabulary Volume Mass Density Speed Distance Time Pressure Force Litres Millilitres Kilograms Grams Miles Kilometres
How to solve problems involving speed Sue drives a distance of 11 miles. She drives for a quarter of an hour. Calculate Sue’s average speed. Give your answer in miles per hour. Speed = 44 m/hr Distance = 11 miles Time = 15 minutes; 0. 25 hours
How to solve problems involving mass A silver chain has a volume of 5 cm 3. The density of silver is 10. 5 grams per cm 3. Work out the mass of the silver chain. Mass = 10. 5 × 5 Mass = 52. 5 g Volume = 5 cm 3 Density = 10. 5 g/cm 3
Solve the following problems – now you try. . . 1. A lobster creeps 10 m along the sea bed in 5 minutes. Find its average speed. 3. 3 cm/s 2. A car cruises at an average speed of 50 miles per hour. How much time will it take to go 600 miles? 12 hours 3. The mass of 5 m 3 of copper is 44800 kg Work out the density of the copper. 8960 kg/m 3 4. The density of concrete is 2. 3 g/cm 3. Work out the mass of a piece of concrete with a volume of 20 cm 3. 46 g
Problem Solving and Reasoning Caleb rides his motorcycle 216 km with a constant speed of 96 km/h and another 124 km with a constant speed of 45 km/h. How much time in total does he take to travel these distances? Time = 2. 75 or 2 hrs 45 min Time = 2. 25 or 2 hrs 15 min Total time taken = 2 hrs 15 min + 2 hrs 45 min = 5 hrs
Problem Solving and Reasoning An ice hockey puck is in the shape of a cylinder with a radius of 3. 8 cm, and a thickness of 2. 5 cm. It is made out of rubber with a density of 1. 5 grams per cm 3. Work out the mass of the ice hockey puck. Give your answer correct to 3 significant figures. Volume of cylinder = πr 2 h Volume of cylinder = π3. 82 × 2. 5 Volume of cylinder = 113. 4114948 Mass = Density × Volume Mass = 1. 5 × 113. 4114948 Mass = 170. 1172422 Mass = 170 g (3 sig fig)
Reason and explain True or false: 1. Mo Farah runs 10000 m in 13 minutes. What is his speed in m/s? The answer is 769 m/s 2. The density of juice is 4 grams per cm 3. The density of water is 1 gram per cm 3. 315 cm 3 of drink is made by mixing 15 cm 3 of juice with 300 cm 3 of water. Work out the density of the drink. The answer is 1. 14 g/cm 3
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