MENTAL ARITHMETIC.

1. To find the value of a dozen articles.

RULE.-Take the price in pence as shillings, and for every farthing add 3 pence to the value.

Example 1.-12 lb. of Meat at 8d. per lb.

The price in pence, taken as shillings, is 8 shillings.

Example 2.-A dozen yards of Tape, at 54d per yard.

5 pence, taken as 5s., to which add 6d. for the d., gives the value, 5s. 6d.

Example 3.-How much will a dozen lb. of Coffee come to, at 2s. 8 d. per lb. ?

2s. 8d.

32d., taken as shillings, 32s.; and 9d. added thereto for d. 32s. 9d. £1. 12s. 9d.

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EXERCISES.

1. 12 lb. of moist Sugar, at 7d. per lb.
2. 12 lb. of Loaf Sugar, at 11d per lb.
3. 12 yards of Cotton, at 14d per yard.
4. 12 oz. of Nutmegs at 9d. per oz.
5. 12 lb. of Beef, at 101d. per lb.

6. 12 pints of Wine, at 1s. 24d. per pint.

7. 12 lb. of Wax Candles, at 1s. 54d. per lb.

8. 12 lb. of Coffee, at 2s. 3d. per lb.

9. A dozen pair of Gloves, at 3s. 7 d. per pair. 10. A dozen of Wine, at 4s. 3 d. per bottle. 11. A dozen pairs of Shoes, at 6s. 74d. per pair. 12. A dozen Legs of Mutton, at 9s. 10 d. each.

MENTAL ARITHMETIC.

1. To find the value of a dozen articles.

RULE.-Take the price in pence as shillings, and for every farting

add 3 pence to the value.

Example 1.-12 lb. of Meat at 8d. per lb.

The price in pence, taken as shillings, is & shillings

2. To find the value of any number of Dozens.

RULE. Find the value of one dozen, and multiply by the given number.

Example 1.-4 dozens of Slates, at 84d. each.

Calculated mentally thus:-1 dozen, at 83d., is 8s. 6d., (by the preceding Rule), and 8s. 6d. multiplied by 4=£1. 14s., the value.

Example 2.-60 pairs of Stockings, at 2s. 3d. per pair.

1 dozen at 2s. 3d,=27d.,=27s. and 27s. ×5=135s.=£6. 15s., the value.

Example 3.-132 yards, at 3s. 4 d. per yard.

1 dozen at 40d.=40s. 6d., and £2. Os. 6d. multiplied by 11 =£22. 5s. 6d.

EXERCISES.

13. 24 yards of Ribbon, at 5d. per yard.
14. 4 dozens of Books, at 8d. each.
15. 72 Lemons, at 2d. each.

16. 5 dozens of Inkstands, at 3 d. each.
17. 8 dozens of Copy-books, at 9d. each.
18. 36 pints of Oil, at 1s. 103d. per pint.
19. 84 lb. of Sugar, at 74d. per lb.

20. 9 dozens of Pigeons, at 14 d. each.

21. 96 lb. of Tobacco, at 1s. 8d. per lb.

22. 132 bushels of Oats, at 1s. 3d. per bushel.

23. 10 dozens of Knives, at 9 d. each.

24. A gross of Rulers, at 16d. each.

3. To find the value of a Score.

RULE. If the price be shillings only, take the shillings as pounds. Example 1.-20 books at 6s. each £6.

Example 2.-A score of yards, at 17s. each £17.

If the price contain pence also, multiply the pence by 20, and find the shillings, which add to the pounds.