130
Expressions with two operations
Textbook: Part 4, lesson 121, pp. 12–13
GoalCalculate two-operation expressions with multiplication and division from left to right.
New words
two-operation expression · ikki amalli ifodaleft to right · chapdan o‘nggavalue · qiymattimes as many · marta ko‘p
Explanation
If an expression has only multiplication and division, the operations go from left to right. 6 × 3 : 9: first 6 × 3 = 18, then 18 : 9 = 2. 21 : 3 × 2: first 21 : 3 = 7, then 7 × 2 = 14. “N times as many” means multiply, “N times fewer” means divide.
Worked examples
6 × 3 : 9 = 18 : 9 = 2.
25 : 5 × 7 = 5 × 7 = 35.
Class activity
“Operation chain”: children stand in a circle. The first says “3 × 4”, the next adds “: 2”, the third adds “× 5”… Each child says the result aloud: 12, 6, 30…
Practice
1
3 × 4 : 2 = ?
6
2
21 : 3 × 2 = ?
14
3
5 × 4 : 10 = ?
2
4
5 apple saplings were planted in a school garden. There are 4 times as many pear saplings, and peach saplings are 2 times fewer than pears. How many peach saplings are there?
10