32
Multiplying a multi-digit number by a three-digit number
Textbook: Part 1, lesson 32, pp. 99–101
GoalMultiply a multi-digit number by a three-digit number in a column.
New words
three-digit factor · uch xonali ko‘paytuvchihundreds · yuzliklarconvenient multiplication · qulay ko‘paytirishequation · tenglama
Explanation
To multiply by a three-digit number, multiply by its ones, tens and hundreds in turn. Each product is written one place further left. Add all the products. It is convenient to put the larger number on top. Remember: 2 × 5 = 10, 4 × 25 = 100, 8 × 125 = 1 000 – grouping such factors makes calculation easier.
Worked examples
1 523 × 214 = 1 523 × 200 + 1 523 × 14 = 304 600 + 21 322 = 325 922.
4 236 × 125 = 4 236 × 100 + 4 236 × 25 = 423 600 + 105 900 = 529 500.
Class activity
“Handy pairs”: cards show 2, 5, 4, 25, 8, 125. Children find pairs whose product is 10, 100 or 1 000 and use them to build easy problems.
Practice
1
623 × 148 = ?
92204
2
Calculate conveniently: 125 × 8 × 37.
37000
3
A school needs 216 desks. One desk costs 348 thousand so‘m. How many thousand so‘m is the total?
75168
4
(x + 4 860) : 316 = 25. Find x.
3040
5
Calculate conveniently: 8 306 × 25 × 4.
830600