37
Price, quantity and cost
Textbook: Part 1, lesson 37, pp. 114–116
GoalKnow how price, quantity and cost are related and use this in problems.
New words
price · narxquantity · miqdorcost (total value) · qiymattable · jadval
Explanation
Cost = price × quantity, that is C = a × n. To find the price, divide the cost by the quantity: a = C : n. To find the quantity, divide the cost by the price: n = C : a. Price is measured in so‘m per piece, per kg, per m and so on. A table makes a problem easier to understand.
Worked examples
One notebook costs 700 so‘m, 8 notebooks: C = 700 × 8 = 5 600 so‘m. Grapes at 18 600 so‘m/kg, 6 kg: 111 600 so‘m.
4 m of ribbon cost 36 000 so‘m: a = 36 000 : 4 = 9 000 so‘m/m. Notebooks at 2 500 so‘m each, total 75 000 so‘m: n = 75 000 : 2 500 = 30.
Class activity
“Little market”: five “products” with price tags are set out. Each child makes a list, chooses quantities and records the total cost in a table.
Practice
1
One notebook costs 700 so‘m. How much do 8 notebooks cost?
5600
2
Grapes cost 18 600 so‘m/kg. How much do 6 kg cost?
111600
3
Notebooks cost 2 500 so‘m each. If 75 000 so‘m was paid in total, how many notebooks were bought?
30
4
4 m of ribbon cost 36 000 so‘m. How much is 1 m of ribbon?
9000
5
6 chocolates at 9 000 so‘m and 4 juices at 14 000 so‘m are bought. How much is left of 150 000 so‘m?
40000
6
One pen costs a so‘m. If n = 70 and a = 2 600, find C = a × n.
182000