123
Solving cost problems (continued)
Textbook: Part 4, lesson 123, pp. 40–42
GoalCost problems with two kinds of goods and with change; diagrams and tables.
New words
change · qaytimin total · jamigoods · tovarpayment · to‘lov
Explanation
If a problem has two kinds of goods, we find the cost of each separately and then add. If the total cost and the cost of one item are known, we find the other by subtraction. Change = money given – cost of the purchase. Writing the condition in a table with columns p, n, C makes the problem clear.
Worked examples
A farmer sold 5 kg of carrots at 3 000 sum/kg and 4 kg of onions at 2 500 sum/kg. Income: 3 000 × 5 + 2 500 × 4 = 15 000 + 10 000 = 25 000 sum.
A loaf and 3 samsas cost 15 000 sum; the loaf costs 3 000 sum. The samsas cost 15 000 – 3 000 = 12 000, so one samsa costs 12 000 : 3 = 4 000 sum.
Class activity
“Market stall”: groups make a price list (3–4 products). Another group names a “shopping basket”, and the sellers work out the total cost and the change from 100 000 sum.
Practice
1
Madina bought 2 kg of apples (11 000 sum/kg) and 3 kg of pears (14 000 sum/kg). How many sum did she pay in total?
64000
2
A large cake and 5 pastries cost 95 000 sum. The cake costs 70 000 sum. How many sum does one pastry cost?
5000
3
Aziza gave the seller 100 000 sum and bought 3 kg of grapes (22 000 sum/kg). How many sum is her change?
34000
4
Juice costs 7 000 sum/piece. Sardor bought 7 pieces and gave 50 000 sum. How many sum is his change?
1000