28
Economics word problems
Textbook: Part 1, lesson 28, pp. 110–111
GoalKnow the link between price, quantity and total cost (C = p · n); solve economics word problems.
New words
price · narxquantity · miqdortotal cost · jami to‘langan puldiscount · chegirma
Explanation
To find the total paid for a purchase, multiply the price by the quantity: C = p · n. The rule for an unknown factor gives p = C : n (price) and n = C : p (quantity). Economics problems often involve several goods, gifts or discounts. Then we find the payment for each good separately and add them. For example, in a “buy two, get the third free” offer only 2 of 3 items are paid for. We always check the result against the money available, asking “is it enough?”.
Worked examples
1 kg of grapes costs 9 500 so‘m. 4 kg cost C = 9 500 × 4 = 38 000 so‘m. If 8 kg of fruit cost 56 000 so‘m, then p = 56 000 : 8 = 7 000 so‘m.
A notebook costs 5 000 so‘m. With 50 000 so‘m we can buy n = 50 000 : 5 000 = 10 notebooks. 4 notebooks and 3 pens (2 000 so‘m each): 4 × 5 000 + 3 × 2 000 = 26 000 so‘m.
Class activity
“Mini shop”: pupils play seller and buyer with price tags and calculate the total and the change for 3 goods.
Practice
1
1 kg of apples costs 7 400 so‘m. How much do 5 kg cost?
37000
2
63 000 so‘m was paid for 9 kg of cherries. What is the price of 1 kg?
7000
3
A shop offers “buy two, get the third free”. One item costs 8 000 so‘m and you have 60 000 so‘m. What is the largest number of items you can get?
10 items: 9 items (three triples) cost 6 × 8 000 = 48 000 so‘m, one more costs 8 000 so‘m, total 56 000 so‘m.
4
Why do we divide the total by the price to find the quantity?
C = p · n, so n = C : p: we find how many times the price fits into the total.