22
Adding and subtracting: word problems
Textbook: Part 1, lesson 22, pp. 67–69
GoalSolve word problems with addition and subtraction of multi-digit numbers.
New words
word problem · masalacondition · shartquestion · savolwriting an expression · ifoda tuzish
Explanation
To solve a word problem, first read the condition carefully and decide what is known and what is asked. Then write an expression or equation, calculate it and check the answer against the question. “How many more” leads to addition and “how many fewer” to subtraction.
Worked examples
On day one 412 000 l of fuel arrived, on day two 135 000 l less. Day two: 277 000 l; in two days 412 000 + 277 000 = 689 000 l.
The first class has 24 pupils, the second has 9 more – 33, the third has 6 fewer than the second – 27. Total: 84 pupils.
Class activity
“Problem workshop”: groups invent a problem with three pieces of data (using 5–6 digit numbers) and give it to another group to solve.
Practice
1
Yesterday 412 000 l of fuel was delivered, today 135 000 l less. How many litres were delivered over the two days?
689000
2
A mountain peak is at 4 120 m and a camp at 2 875 m. How many metres lower is the camp than the peak?
1245
3
A bike race has three stages. The first is 4 260 m, the second is 1 580 m shorter, the third is 905 m longer than the first. How long is the whole race in metres?
12105
4
Three classes went on a school trip. 24 pupils came from the first class, 9 more from the second, and 6 fewer than the second from the third. How many pupils in all?
84
5
The first group has 18 more people than the second. How many must move from the first to the second so the groups are equal?
9