2. Find the area of each of the following triangles in square feet; base of each 100 feet, altitude 60 feet.

4444

3. Mark in each of the following eleven triangles its area in square feet; altitude of each, 60 ft.

4. Find the area of each of the following four triangles in square feet; altitude of each, 60 ft.

4444

50

60

70

40

5. Find the area of each of the following four parallelograms; altitude of each, 60 ft.

6. Find the area of each of the following trapezoids; altitude of each, 60 ft. The number of square feet in each is equal to 60 multiplied by what?

7. One diagonal of each of the following quadrilaterals measures 100 feet. The perpendiculars let fall on this diagonal from the opposite corners measure 30 ft. and 40 ft., respectively. Find the area of each in square feet.

30

100

30

100

8. Cut from a strip of paper, AB, two inches wide, a rectangle, a rhombus, and a rhomboid, as given in the accompanying diagram. Show that the three parallelograms are equal in surface.

9. Cut from a strip of paper, two inches wide, three trapezoids. Make one parallel side of each 2 inches long, and the other parallel side 3 inches long. Divide up each trapezoid in such a way as to show that its surface is equal to that of a rectangle 21 in. by 2 in.

1. How many cubic feet are there in a block of granite whose base is 4 feet square, and whose height is 6 feet?

2. Find the value of the above block at 60 per cubic foot, and the cost of polishing its six faces at 60 per square foot.

3. A contractor charged 30 per cubic yard for digging a cellar 21 feet wide, 60 feet long, 9 feet deep. What was the amount of his bill?

4. What will be the cost of cementing the floor of the above cellar at 75 per square yard? Deduct from the given dimensions the thickness of the four walls, eighteen inches each. Make a diagram.

5. A cubic foot of water weighs 1,000 ounces. Marble is 2.8 times as heavy. Calculate the weight, in tons, of a marble shaft 4 feet square and 12 feet high.

(Cancel.)

6. A carpenter is making a cubical box whose inside measurement is 1 foot. Each side consists of a single piece of wood 1 inch thick. Give the dimensions, in inches, of each of the six pieces used.

7. How many pounds avoirdupois would there be in a brick of pure gold 8 x 4 x 2 inches, gold being 19.4 times as heavy as water?

8. Find the weight in pounds of a cord of pine wood, which is .66 times as heavy as water.

9. A cube of marble, 12 inches on a side, is enclosed for transportation in a tightly fitting wooden box made of material one inch thick. What are the outside dimensions of the box? How many cubic inches in the wood and the marble together? How many cubic inches are there of each?

10. An iron cube 2 feet long weighs 2 tons. How many times as heavy as water is iron? Calculate the weight of an iron cube 1 foot long. Of one 3 feet long.

CHAPTER XII.

SIMPLE AND COMPOUND INTEREST. - DISCOUNT. — CAUSE AND EFFECT. - PARTNERSHIP. - BONDS AND STOCKS.

- EXCHANGE. — LONGITUDE AND TIME.

AND VOLUMES.

- SURFACES

TO FIND PRINCIPAL, RATE, OR TIME.

931. At what rate per cent will $723.60 amount to $759.78

932. In what time will $85.50 produce $8.17 interest, at 4 per cent?

933. Slate Exercises.

Find rate, time, etc.

1. Principal, $2,000; time, 3 yr.; interest, $300. Rate? 2. Principal, $1,800; rate, 4%; interest, $144. Time? 3. Time, 8 mo.; rate, 41%; interest, $2.88. Principal? 4. Principal, $38; time, 2 yr.; amount, $40.28. Rate? 5. Principal, $140; rate, 31%; time, 3 mo. 15 da. Interest? 6. Amount, $39.60; rate, 4%; time, 2 yr. 6 mo. Principal? 7. Amount, $484.15; rate, 31%; principal, $460. Time? 8. Principal, $39.60; rate, 4%; time, 1 yr. 7 mo. 15 da. Amount?

9. Time, 8 yr.; rate, 3%; amount, $6,200. Principal? 10. Principal, $7,548; time, 3 mo. 5 da.; interest, $119.51. Rate?

11. Principal, $9,000; rate, 4%; interest, $632. Time?

12. Time, 2 yr. 3 mo. 20 da.; rate, 5%; amount, $160.60. Principal?

13. Principal, $756; rate, 31%; time, 3 yr. 4 mo. 20 da. Interest?

14. Principal, $120; time, 1 yr. 2 mo. 15 da.; interest, $4.35. Rate?

15. Amount, $97.57; rate, 4%; interest, $7.57. Time?

16. Time, 3 yr. 8 mo. 19 da; rate, 41%; amount, $93.39. Principal?

17. Principal, $1,848; rate, 33%; time, 4 yr. 9 mo. 25 da. Amount?

18. Rate, 5%; time, 4 yr. 6 mo. 23 da.; interest, $16.43 Principal?