Q1.
Find the quotient by converting the denominator into 1, 10, 100 or 1000 and verify the solution by the long division method (division by place value). (a) 18/5 (b) 415/4 (c) 1217/2 (d) 4827/8
Answer
Find the number that turns the denominator into 10, 100 or 1000, then multiply the top by the same number.
(a) 5 × 2 = 10
18/5 = (18 × 2)/(5 × 2) = 36/10 = 3.6
(b) 4 × 25 = 100
415/4 = (415 × 25)/(4 × 25) = 10375/100 = 103.75
(c) 2 × 5 = 10
1217/2 = (1217 × 5)/(2 × 5) = 6085/10 = 608.5
(d) 8 × 125 = 1000
4827/8 = (4827 × 125)/(8 × 125) = 603375/1000 = 603.375
18/5 = (18 × 2)/(5 × 2) = 36/10 = 3.6
(b) 4 × 25 = 100
415/4 = (415 × 25)/(4 × 25) = 10375/100 = 103.75
(c) 2 × 5 = 10
1217/2 = (1217 × 5)/(2 × 5) = 6085/10 = 608.5
(d) 8 × 125 = 1000
4827/8 = (4827 × 125)/(8 × 125) = 603375/1000 = 603.375
Verification by long division (the last steps only):
| Division | Whole part | Regrouping | Quotient |
|---|---|---|---|
| 18 ÷ 5 | 3, remainder 3 | 3 Ones → 30 Tenths; 30 ÷ 5 = 6 Tenths | 3.6 |
| 415 ÷ 4 | 103, remainder 3 | 30 Tenths → 7 Tenths r 2; 20 Hundredths → 5 | 103.75 |
| 1217 ÷ 2 | 608, remainder 1 | 10 Tenths ÷ 2 = 5 Tenths | 608.5 |
| 4827 ÷ 8 | 603, remainder 3 | 30 Tenths → 3 r 6; 60 Hund. → 7 r 4; 40 Thou. → 5 | 603.375 |
Why it happens: 5, 4, 2 and 8 are all built only from 2s and 5s, so each of them divides some power of ten exactly. That is why all four quotients stop after a few decimal places.