416 - 41 = 375, 375900 = 512. Ans. 5⁄12.
To add, subtract, multiply and divide circulates, reduce them to common fractions, then apply the respective rules.
Short Methods in Merchandising
When one of the numbers is an aliquot part of 100, the process of multiplication and division can often be very much shortened, as shown below.
Find cost of 27 yards of goods at 162⁄3c ($1⁄6) per yard. At $1 per yard, 27 yards cost $27; at $1⁄6, (27 ÷ 6), $41⁄2. Ans. $41⁄2.
Find cost of a bale of cotton, 528 pounds at 81⁄3c ($1⁄12) per pound. At $1 per pound, 528 pounds cost $528; at $1⁄12 (528 ÷ 12) $44. Ans. $44.
Find cost of 1845 pounds of iron, at 31⁄3c ($1⁄30) per pound. Take 1⁄30 of 1845, since 31⁄3c is 1⁄30 of $1. (1845 ÷ 30 = 611⁄2). Ans. $611⁄2.
Find cost of 16 pounds of butter at 371⁄2c ($3⁄8) per pound. Here we take 3⁄8 of 16. Say 1⁄8 of 16 is 2, and 3⁄8 is (2 × 3) 6. Or say 3 times 16 is 48, and 1⁄8 of 48 is 6. Ans. $6.
Find cost of 171⁄2 bushels of apples at 75c ($3⁄4) per bushel. The shortest way to find 3⁄4 of $17.50 is to diminish it by 1⁄4 of itself.
| 4 | ) | 17 | .50 | at $1 | |
| 3 | .371⁄2 | at $1⁄4 | |||
| 13 | .121⁄2 | at $3⁄4 | |||