132
Comparing the values of expressions
Textbook Part 4, pp. 44–45
GoalCompare expressions; guess the value of a letter; write a letter expression for a problem.
New words
to guess / estimate · taxmin qilmoqkilometre · kmmidday · kunning yarmi
Explanation
To compare two expressions, find each value and compare the results. Sometimes you can guess the letter’s value: “the sum of x and 6 equals the difference of 10 and x” — if x = 2, then 2 + 6 = 8 and 10 − 2 = 8 ✓.
Worked examples
Aziz must walk 6 km a day and has walked x km today. Still to go: 6 − x km.
A traveller left at midday (12:00) and came back at midnight (24:00): 12 hours away.
Class activity
Balance game: the left pan has “x + 3”, the right pan 9 pebbles. What must x be to balance? Children try it with pebbles.
Practice
1
Compare: 25 + 4 ... 30 − 1
=
2
Tashkent to Qibray is t km and Qibray to Chirchiq m km. Total?
t + m
3
If x + 3 = 9, then x = ?
6
4
Compare: 46 − 20 ... 46 − 30
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