58
Long division by a three-digit number (practice)
Textbook: Part 2, lesson 58, pp. 60–62
GoalPractising division: zeros in the quotient, comparing and equations.
New words
comparing · taqqoslashequation · tenglamaunknown · noma’lumroot · ildiz
Explanation
A 0 may appear in the middle or at the end of the quotient: 40 640 : 127 = 320. Comparing without calculating: with the same dividend, the bigger the divisor, the smaller the quotient. To find an unknown factor, divide the product by the known factor: x × 36 = 1 260, x = 1 260 : 36.
Worked examples
40 640 : 127: 406 : 127 = 3 (381, remainder 25), 254 : 127 = 2, 0 : 127 = 0. The quotient is 320.
9 180 : 135 = 68, because 135 × 68 = 9 180.
Class activity
“Compare without calculating”: children put a sign (<, >) between pairs of examples on cards (for instance 12 312 : 27 and 12 312 : 54) without calculating, then check by calculating.
Practice
1
12 312 : 27 = ?
456
2
12 312 : 54 = ?
228
3
Without calculating, which is bigger: 18 000 : 30 or 18 000 : 60?
18 000 : 30 (the divisor is smaller). Check: 600 and 300
4
98 000 : 245 = ?
400
5
Find x in the equation x × 36 = 1 260.
35
6
48 notebooks of the same price cost 52 800 so‘m. How much does one notebook cost, in so‘m?
1100