141
Year review: measures, volume, price and rate of work
Textbook: Part 4, lesson 141, pp. 95–96
GoalYear review: measures of length, mass and volume, the volume of a cuboid, the price and rate-of-work formulas.
New words
unit of measure · o‘lchov birligivolume · hajmmass · massalength · uzunlik
Explanation
When calculating with measures we first convert them to the same unit: 1 km = 1 000 m, 1 kg = 1 000 g, 1 t = 1 000 kg, 1 m = 10 dm = 100 cm. The volume of a cuboid is V = a × b × c (cm³, dm³, m³); 1 dm³ = 1 l. Cost C = p × n and amount of work A = w × t – in both we multiply the amount for one unit by the number of units.
Worked examples
3 km 250 m + 1 km 850 m = 3 250 m + 1 850 m = 5 100 m = 5 km 100 m.
A box is 8 cm long, 5 cm wide and 3 cm high. Its volume is V = 8 × 5 × 3 = 120 cm³.
Class activity
“Measure market”: children measure the length, mass or volume of classroom objects, write the result in two units (for example cm and mm) and have a partner check it.
Practice
1
Calculate 4 kg 300 g + 2 kg 900 g in grams.
7200
2
Calculate 2 t 450 kg − 1 t 800 kg in kilograms.
650
3
A cuboid-shaped tank is 4 dm long, 3 dm wide and 5 dm high. How many litres of water does it hold?
60
4
One pencil costs 2 500 sum. For how many pencils are 17 500 sum paid?
7
5
A pump delivers 45 l of water per minute. How many litres does it deliver in 12 minutes?
540