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Unit review
Textbook: Part 4, pp. 55–56
GoalReview of formulas: movement, cost, rate of work, area and perimeter of a rectangle.
New words
formula · formulaletter symbol · harf belgisiarea · yuzperimeter · perimetr
Explanation
A formula is a short way of writing how quantities are connected. Movement: s = v × t (distance, speed, time). Cost: C = p × n (cost, price, quantity). Work: A = w × t (amount of work, rate, time). In all three we multiply “the amount per one unit” by “the number of units”. For a rectangle: area S = a × b, perimeter P = (a + b) × 2.
Worked examples
A walker went at 4 km/h for 3 hours: s = 4 × 3 = 12 km. Then he cycled at 12 km/h for 2 hours: s = 12 × 2 = 24 km. Total 12 + 24 = 36 km.
A rectangle is 9 cm long and 4 cm wide. Its area is S = 9 × 4 = 36 cm² and its perimeter is P = (9 + 4) × 2 = 26 cm.
Class activity
“Formula builders”: four groups each build one formula (s = v × t, C = p × n, A = w × t, S = a × b) from letter cards and make up one problem for it.
Practice
1
A walker went at 5 km/h for 2 hours and then cycled at 15 km/h for 3 hours. How many kilometres did he travel in total?
55
2
A book and 3 notebooks cost 30 000 sum. The book costs 18 000 sum. How many sum does one notebook cost?
4000
3
A machine makes 24 parts per hour. How many parts does it make in 7 hours?
168
4
A rectangle is 12 cm long and 5 cm wide. What is its area in cm²?
60
5
What is the perimeter of the same rectangle in cm?
34