39
Ecology problems
Textbook: Part 1, lesson 39, pp. 120–122
GoalSolve ecology problems using the “find one first” method.
New words
ecology · ekologiyawaste paper · makulaturarecycling · qayta ishlashsaving · tejash
Explanation
In ecology problems we often first find the amount for one unit and then multiply. For example, if 2 t of broken glass gives 1 600 kg of new glass, then 1 t gives 1 600 : 2 = 800 kg and 5 t gives 800 × 5 = 4 000 kg. Things we can use many times save money and protect nature in the long run.
Worked examples
2 t → 1 600 kg; 1 t → 800 kg; 5 t → 4 000 kg of new glass.
A reusable water bottle costs 45 000 sum and bottled water 2 500 sum. At 3 bottles a week, 10 weeks need 30 bottles = 75 000 sum; with the reusable bottle you save 75 000 − 45 000 = 30 000 sum.
Class activity
“Clean yard”: with the teacher and adults supervising and wearing gloves, children collect paper litter in the school yard, weigh it and make a class table.
Practice
1
2 t of broken glass gives 1 600 kg of new glass. How many kg does 5 t give?
4000
2
A reusable water bottle costs 45 000 sum and one bottle of water 2 500 sum. A child used to buy 3 bottles a week. How many sum does the reusable bottle save in 10 weeks?
30000
3
Five pupils collected 24 kg, 18 kg, 30 kg, 12 kg and 21 kg of waste paper. What is the average in kg?
21
4
The school set a goal of 120 kg of waste paper. Classes 4A, 4B, 4D collected 28 kg, 33 kg and 25 kg. How many kg more are needed?
34