A grocer mixes 2 cwt. 15 lbs. of sugar at 11d. per pound with 14 cwt. 3 lbs. at 5d. per pound. At how much per pound must he sell the mixture so as not to lose by mixing them?
Answer, 5d. ¾ ¹⁵³/₉₀₅.
230. There is a convenient method of multiplication called Practice. Suppose I ask, How much do 153 tons cost if each ton cost £2. 15. 7½? It is plain that if this sum be multiplied by 153, the product is the price of the whole. But this is also evident, that, if I buy 153 tons at £2. 15. 7½ each ton, payment may be made by first putting down £2 for each ton, then 10s. for each, then 5s., then 6d., and then 1½d. These sums together make up £2. 15. 7½, and the reason for this separation of £2. 15 . 7½ into different parts will be soon apparent. The process may be carried on as follows:
1. 153 tons, at £2 each ton, will cost
£306 0 0
2. Since 10s. is £½, 153 tons, at 10s. each, will cost £15³/₂, which is
76 10 0
3. Since 5s. is ½ of 10s., 153 tons, at 5s., will cost half as much as the same number at 10s. each, that is, ½ of £76 . 10, which is
38 5 0
4. Since 6d. is ⅒ of 5s., 153 tons, at 6d. each, will cost ⅒ of what the same number costs at 5s. each, that is, ⅒ of £38 . 5, which is