36
Solving word problems (practice)
Textbook: Part 1, lesson 36, pp. 111–113
GoalOperations with units of area; income, expense and profit; comparing shops.
New words
income (revenue) · daromadexpense (cost) · xarajatprofit · foydasquare decimetre · kvadrat detsimetr
Explanation
1 m² = 100 dm². To calculate with units of area we convert to one unit, for example square decimetres: 4 m² 13 dm² = 413 dm². Income is the money received from selling goods, expense is the money spent making them, profit is the difference: profit = income − expense. To compare shops we work out the cost of the whole purchase in each.
Worked examples
12 m² 40 dm² + 7 m² 85 dm² − 5 m² 60 dm² = 1240 dm² + 785 dm² − 560 dm² = 1465 dm².
A bag costing 85 000 so‘m to make and sold for 140 000 gives a profit of 55 000 so‘m; from 15 bags 825 000 so‘m.
Class activity
“Small business”: groups set a “production” price and a selling price for a product (for example a paper flower) and work out the profit from selling 10.
Practice
1
12 m² 40 dm² + 7 m² 85 dm² − 5 m² 60 dm². Give the answer in dm².
1465
2
Gulnora sews bags: each costs her 85 000 so‘m and sells for 140 000. What is her profit from selling 15 bags?
825000
3
5 m of silk and 3 m of taffeta are bought. Shop A: silk 70 000, taffeta 30 000 so‘m per m. Shop B: silk 68 000, taffeta 34 000 so‘m per m. Which shop is cheaper?
Shop A: 440 000 so‘m, shop B: 442 000 so‘m – A is cheaper.
4
Compare 254 × 63 and 254 × 630 without calculating (<, >, =).
<
5
Two pieces of cloth measure 35 cm × 18 cm and 27 cm × 24 cm. Which has the greater area?
The second: 630 cm² < 648 cm²