139
Year review: long multiplication and division
Textbook: Part 4, lesson 139, pp. 91–92
GoalYear review: multiplying by multi-digit numbers, long division, division with a remainder.
New words
product · ko‘paytmaquotient · bo‘linmaremainder · qoldiqlong division · burchakli bo‘lish
Explanation
When multiplying by a two-digit number we multiply by each digit of the multiplier separately and add the partial products, placing them in the right places. In long division we find the digits of the quotient one by one: divide, multiply, subtract, bring down the next digit. The remainder is always smaller than the divisor. Check: quotient × divisor + remainder = dividend.
Worked examples
245 × 38: 245 × 8 = 1 960, 245 × 30 = 7 350, total 1 960 + 7 350 = 9 310.
3 456 : 18 = 192. Check: 192 × 18 = 1 920 + 1 536 = 3 456. 500 : 24 = 20 remainder 20, because 24 × 20 = 480 and 500 − 480 = 20.
Class activity
“Column contest”: two teams take turns solving one column calculation (multiplication or division) at the board. A correct, checked answer scores 1 point.
Practice
1
Calculate 126 × 305.
38430
2
Calculate 7 200 : 80.
90
3
A factory makes 1 250 bottles a day. How many bottles does it make in 28 days?
35000
4
Divide 500 : 24.
20 remainder 20
5
Calculate 4 096 : 16 and check by multiplying.
256