87
Problem solving (practice)
Textbook: Part 3, lesson 87, pp. 49–51
GoalMore problem solving: comparing fractions, checking statements, parts of a whole and rate of work.
New words
statement · tasdiqtrue / false · to‘g‘ri / noto‘g‘rirate of work · unumdorlikpage · bet
Explanation
When solving problems, first read the condition and decide what to find. To check statements about fractions, use the comparison rules (same denominators or same numerators). When people work together, add their daily work: total work : combined rate = time.
Worked examples
A book has 160 pages. Day 1: 3/8 read: 160 : 8 × 3 = 60 pages; day 2: 1/4: 160 : 4 = 40 pages; left 160 − 60 − 40 = 60 pages.
“1/4 < 1/7” is false: the numerators are equal and the smaller denominator gives the greater fraction, so 1/4 > 1/7.
Class activity
“True or false?”: the teacher reads statements about fractions. Children stand up if true and sit down if false, then explain why using fractions.
Practice
1
A book has 240 pages. On day 1, 3/8 of it was read and on day 2, 1/4. How many pages are still unread?
90
2
Find the greatest of 4/9, 4/5, 4/7.
4/5
3
Is the statement “one fifth is less than one ninth” true?
no, 1/5 > 1/9
4
One weaver makes 40 m of cloth a day and another 60 m a day. How many days do they need together for 1 000 m?
10
5
Find the smallest of 5/6, 5/12, 5/8.
5/12