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CASE 2. When the two extremes and number of terms are given, and the common difference of all the terms required;
RULE. Divide the difference of the extremes by the number of terms, less one, the quotient will be the common difference.
EXAMPLES. 1 Admit a debt be discharged at 16 several payments in
arithmetical progression; the first to be 141. the last 1001. .. what is the common difference, and what each payment, and the whole debt ?
f. s. d.
19 14 8 = second.
25 9 4 = third, &c. 14+100x8=9121. the whole debt. 2 A man had 10 sons, whose several ages differed alike; the youngest was 3 years old, and the eldest 48 ; what was the common difference of their ages ? ? answer 5 years.
3 There are 21 persons, whose ages are equally distant from each other; the youngest 20 years old, and the eldest 60; what is the common difference of their ages, and the age of each person ? answer common difference 2 years.
* 20 the age of the first person. 20+2-22 of the second.
22+2=24 of the third, &c. 4 A footman is to travel from Philadelphia to a certain place in 19 days, and to go but six miles the first day, increasing every day by an equal excess, so that the last day's journey may be 60 miles; what is the common difference, and distance of the journey?
ensuper ŞCommon difference 37
· GEOMETRICAL PROGRESSION.
GEOMETRICAL Progression is a series of numbers, increasing by a common multiplier, or decreasing by a common divisor, called the ratio; as, 2, 4, 8, 16, 32, &c. increase by the multiplier, 2; and 32, 16, 8, 4, 2, decrease continually by the divisor 2, &c.
The last term and sum of the series are found by this . .
RULE. · Raise the ratio to the power whose index is one less than the number of terms given, which multiply by the first term, that product is the last term or greater extreme.
Multiply the last term by the ratio, from the product sub- . tract the first term, and divide the remainder by the ratio less one; the quotient will be the sum of the series.
EXAMPLES. 1 Sold 24 yards of Holland, at 2d. for the first yard, 4d. the second, 5d. the third, &c. in a duplicate proportion ; how much do they amount to ?
1 2 3 4 indices,
2 4 8 16 leading terms.' .... ..16
2 first term.;
i 2 Bought
2 Bought 30 bushels of wheat; the firsi bushel for 2d. the second 4d. the third 8d. doubling the price of each preceding bushel for that of the next; query the amount, and price per bushel at an average ?
S 89478481 10s 6d. Amount.
et 2982611 12s 4d. per Bushelst do 3 Sold 15 yards of sattin, the first yard for 1s, the se.
cond for 2s. the third for 4s. &c. what sum did they amount to?
.. . ? answer 16381 78. 4 Admit a goldsınith sold one lb. of gold, at one farthing for the first ounce, a penny for the second, 4d. for the third, &c. in a quadruple proportion'; what did it amount to ? and what did he gain by it, supposing it cost him 4l. per ounce? vais ia
5 58251 8s 5d. Sold for.
answer 3 57771 8s 5d. 1 Gained. 5 What sum would purchase a horse with 4 shoes, and 8 nails in each shoe, at one farthing for the first nail, a half-penny for the second, a penny for the third, &c. doub. ling to the last ?
answer 44739241 5s 3d. Ő Suppose a man wrought 20 days, and received for the first day 4 barley corns, for the second 12, for the third 36, &c. in a triple proportion ; what did the twenty days labour come to, rating the barley at 28. 6d. per bushel ?
answer 17731 7s 6d. Note. 7680 Wheat, or Barley corns, are supposed to make a pint.
7 Sold 30 yards of velvet, at 2 pins for the first yard, A . 6. for the second, 18 for the third, &c. and these disposed
of at one farthing per 100, how much did the velvet amount to ? And whether did the seller gain or lose, and how much, supposing the prime cost of the velvet at 50l. per yard?
521446992921 13s Odi Amount.
em 21446977921 13s Ody Gained. 8 A certain person married his daughter on new year's day, and gave her one guinea towards her portion, promise ing to double it on the first day of every month for one year; what was her portion in sterling money?
inswer 42991 15s. 0 . .
SIMPLE INTEREST–By DecimalS. Note. The ratio is the Interest of 11. for one year, and is thus found.
(100 : 6 :: 1 ,06 &c.
A TABLE OF RATIOS.
..095 F .06 The principal, time, and ratio given, to find the intere and amount. .
to RULE. Multiply the principal, time, and ratio together, the last product will be the interest, commission, brokage, &c. to which add the principal, and the sum will be the amount... Note. In operations of interest by decimals, the money should be in the de
nominations of pounds, or dollars, and the time in years, with their parts (if any) annexed decimally.
: 537,5 Principal.
: 2 What is the interest of 9171 16s. at 5 per cent. per annum for 7 years ?
sanswer 221l 4s 7d. 3 If my correspondent be to have 45 per cent. what will his commission on 3911 17s. come to ?
answer 171 12s 70.1 4 What will be the interest and amount of 5671 10s. in 9 years, at 6 per cent. per annum ?
5 3061 9s. Interest.
answer 3 8731 19s. Amount. 5 What is the interest of 47261 18s 6d.) for 34 years, at ne per cent. per annum?
answer 11587 is 11d. .6 What will 95261 12s 9d. amount to in 12 years and 9 months, at 7 per cent. per annum ? answer 180291 3s 2d.
CASE 1. When several simple quantities and their prices are given, and a mean price of any part of the compound is required.
So is any part of the composition
B ; EXAMPLES. 1 If 19 bushels of wheat at 6s. the bushel, 40 of rye.at 4s. and 12 of barley at Ss. be mixt together; what is a . bushel of this mixture worth?
71 )31014 44 answer. 2 A grocer mixed sugars; 2 C.wt. at 56s. 1С.wt. at 43s. and 2C.wt. at 50s. per C.wt. what is 3C.wt. of this mixture worth ? .
answer 71 13s.