60
Practical tasks
Textbook: Part 2, lesson 60, pp. 66–68
GoalPractical problems: solving multi-step, everyday problems and checking the result.
New words
saving · tejashpoint · ballguess and check · taxmin va tekshirishresult · natija
Explanation
In a practical problem we read the text and split it into steps: what to find first and what next. Saving water: if 6 l flows from a tap each minute, then in 3 minutes 6 × 3 = 18 l flows. In a points problem we pretend every answer is right and divide the gap by how many points one wrong answer costs. At the end we put the answer back into the story to check.
Worked examples
A quiz has 15 questions: +4 for a right answer, −1 for a wrong one. Jasur scored 45. All right would be 60; the gap is 15. One mistake costs 4 + 1 = 5 points, 15 : 5 = 3 mistakes, so 15 − 3 = 12 right answers.
With the tap open while brushing, 18 l flows in 3 minutes. Twice a day for a year (365 days): 18 × 2 × 365 = 13 140 l.
Class activity
“Saving water”: the class makes a table of one day’s water use (brushing teeth, washing hands) and calculates how many litres are saved by turning the tap off.
Practice
1
6 l of water flows from an open tap each minute. If brushing teeth takes 3 minutes, how many litres flow away?
18
2
A child leaves the tap open for 3 minutes twice a day. How many litres flow away in a year (365 days)? (6 l per minute.)
13140
3
A contest has 10 questions. A right answer gives 4 points, a wrong one takes away 2 points. Aziza got 22 points. How many questions did she answer correctly?
7
4
4 560 people live in a neighbourhood. One big tree gives enough oxygen for 3 people. How many trees are needed for everyone?
1520