37
Problem solving: mixed
Textbook: Part 1, lesson 37, pp. 114–116
GoalWrite and evaluate expressions from words; solve price–quantity–cost table problems.
New words
expression · ifodaminuend · kamayuvchisubtrahend · ayriluvchivalue (cost) · qiymat
Explanation
To write an operation given in words as an expression, identify each term. “The first addend is 5 400 and the second is the quotient of 8 100 and 9” gives 5 400 + 8 100 : 9. Division is done before addition. In a table problem one of price a, quantity n and cost C is unknown: C = a × n.
Worked examples
5 400 + 8 100 : 9 = 5 400 + 900 = 6 300.
Potatoes at 4 500 sum/kg, 7 kg: 31 500 sum; onions at 6 000 sum/kg, 3 kg: 18 000 sum. Total 49 500 sum.
Class activity
“Say the expression”: one child writes an expression and the partner reads it in words (“the minuend is …, the subtrahend is …”); then they swap.
Practice
1
The first addend is 5 400 and the second is the quotient of 8 100 and 9. Find the sum.
6300
2
The minuend is the quotient of 14 000 and 40 and the subtrahend is 268. Find the difference.
82
3
How many sum do 7 kg of potatoes (4 500 sum/kg) and 3 kg of onions (6 000 sum/kg) cost together?
49500
4
1 440 books arrived at the school library in 15 and 21 identical boxes. How many books are in each box?
40