157
Unit review: round numbers, multiplication and division
Textbook: Part 4, pp. 66–67
GoalEnd-of-unit review: multiplying and dividing round numbers, multiplying two-digit numbers, word problems.
New words
round number · yaxlit sonreview · takrorlashproduct · ko‘paytmaquotient · bo‘linma
Explanation
Remember: to multiply round numbers, drop the zeros, multiply, put the zeros back (30 × 50 = 1500). To divide, drop equal zeros from both numbers (450 : 50 = 45 : 5 = 9). Multiply a two-digit number by a one-digit number with the distributive law (31 × 3 = 90 + 3 = 93). In a problem, “times fewer” means divide and asking for the total means add.
Worked examples
450 : 45 = 10, because 45 × 10 = 450.
100 : 4 = 25, because 4 × 25 = 100.
Class activity
“Sports-day quiz”: the class splits into two teams. On the board are “sport” cards, each with a problem on the back (12 × 8, 500 : 50…). A correct answer earns a point; the team with most points wins.
Practice
1
450 : 45 = ?
10
2
12 × 8 = ?
96
3
100 : 4 = ?
25
4
31 × 3 = ?
93
5
500 : 50 = ?
10
6
There are 26 footballers and 2 times fewer basketball players. How many footballers and basketball players are there in all?
39