35
Solving word problems
Textbook: Part 1, lesson 35, pp. 108–110
GoalSolve word problems about prices, mass, tables and equations.
New words
number thought of · o‘ylangan sontable · jadvalwriting an equation · tenglama tuzishchecking · tekshirish
Explanation
A table or a diagram helps to record the condition. In “I thought of a number…” problems we call the number x and write an equation. An unknown addend is the sum minus the known addend; an unknown subtrahend is the minuend minus the difference. We check by putting the answer back.
Worked examples
x + 14 500 = 60 × 7 000. 60 × 7 000 = 420 000, x = 420 000 − 14 500 = 405 500.
650 loaves an hour, 8 hours, 30 days: 650 × 8 × 30 = 156 000 loaves.
Class activity
“Guess the number”: pairs hide thought-of numbers and give riddles as equations (for example “I added 500 to my number and got 2 000”). The partner writes and solves an equation.
Practice
1
I thought of a number. Adding 14 500 gives the product of 60 and 7 000. What was my number?
405500
2
Subtracting my number from 250 000 gives the product of 120 and 705. What was my number?
165400
3
6 bricks need 24 kg of clay. How many kg are needed for 1 500 bricks?
6000
4
1 kg of carrots costs 5 400 so‘m and 1 l of milk 9 500 so‘m. 6 kg of carrots and 4 l of milk are bought. How much is left of 100 000 so‘m?
29600
5
For a big pilaf: rice 60 kg, carrots 70 kg, meat 45 kg, oil 18 kg, onions 22 kg. What is the total mass of the ingredients in kg?
215