96. The area of a surface is the number of times that it contains another surface, taken as the unit of measurement. Thus, the statement that the area of a surface is 8 square inches means that a square inch is contained in the surface 8 times.

97. The sum of all the sides of a figure is called its perimeter.

98. Written Exercises.

Find the area of each of the following rectangles in square inches. Find the perimeter of each in feet and inches.

NOTE.-Change each dimension to inches before multiplying.

How many square feet in a rectangle 2 feet long, 1 foot. wide?

How many square feet in a rectangle 6 feet long by 5 feet wide?

How many square feet in a rectangle 9 feet long by 7 feet

wide?

NOTE. The unit in the following examples is the square foot.

100. Written Exercises.

Find the area in square feet of each of the following rectangles. Find the perimeter of each in feet.

NOTE. Change the inches to fractions of a foot.

1. Measure the top of the desk, disregarding fractions. of an inch, and calculate the surface in square inches.

2. Measure the blackboard, and find how many square feet in its surface. (Do not include fractions of a, foot.)

3. Calculate the number of square inches in a pane of glass in the schoolroom window.

4. Find the number of square feet in the floor of the classroom.

5. Find the number of square feet in the classroom ceiling.

6. Estimate the height of the classroom, and calculate the number of square feet in the front wall. 7. In the rear wall. 8. In the right-hand wall. 9. In the left-hand wall.

102. Written Problems.

SUGGESTION. -When the surface is required in square inches, change each dimension to inches; when required in square feet, express each dimension in feet, or in feet and the fraction of a foot; when required in square yards, etc., express each dimension in yards,

etc.

1. How many square feet are there in the surface of a field 125 feet long, 87.5 feet wide?

(1 square foot x 125 x 87.5.)

2. A rug is 2 yards long, 13 yards wide. How many square yards does it contain?

(1 square yard × 2 × 18.)

3. How many square yards are there in a strip of carpet 6 yards long, 27 inches (yard) wide?

4. Find the number of square meters in a room 12 meters long, 9.75 meters wide.

5. At 50 cents per square yard, what will be the cost of the oil-cloth needed to cover a floor 18 feet (6 yards) long, 15 feet (5 yards) wide?

6. What will be the cost, at $1.50 per square yard, of carpeting a room 6 yards long, 15 feet wide?

7. At 3 cents a square foot, how much must be paid for 10 boards, each 16 feet long, foot wide?

8. A field is 30 rods long and 24 rods wide. How many square rods will it contain after a strip 24 rods long and 2 rods wide is taken from it for a road?

9. How many square yards of plastering will be required for a ceiling 18 feet long, 15 feet wide?

10. If a roll of wall paper is 24 feet long and 18 inches wide, how many square yards does it contain?

1. Copy the above, filling in the cost of each item and the total.

In these examples, the total cost of each item should be written in its place without any side calculation. Pupils should be drilled in short, direct methods of computation, being required to omit unnecessary figures.

In No. 2, for instance, 64 is multiplied by 51, as follows:

of 64 is 8; carry this to the product of 5 and 4, making 28; write 8. 5 times 6 are 30, add 2, making 32. Total, 328.

2. Otto Haas buys of Murphy & Cooper 64 pounds of sugar @51; 28 pounds of lard @ 91; 24 pounds of coffee @254; 1 barrel flour @ $5.75; and 12 gallons of molasses @254. Make out the bill.

3. Make out a bill for 10 pairs of men's shoes, at $4.75; 4 pairs of boys' shoes, at $ 1.471; 6 pairs slippers, at $.871; 9 pairs of girls' shoes, at $2.43; 8 pairs of women's shoes, at $3.37.

4. Make out a bill for 81 pounds of ham, at 14 per pound; 31 pounds of beefsteak, at 209; 9 pounds of corned beef, at 12; 101 pounds of chicken, at 244; 12 pounds of roast beef, at 18%.

5. Make out a bill for 14 dozen collars, at $1.50 per dozen; 6 dozen pairs of cuffs, at $2.75 per dozen pairs; 4 dozen shirts, at $9 per dozen; 3 dozen ties, at $2.25 per dozen; 17 dozen pairs of socks, at $2.10 per dozen pairs.

104. Review Exercises. Approximate Answers.

NOTE. These drills are intended to lead a pupil to such an examination of his answers to other problems as will prevent him from being satisfied with one that is very far astray.

It is not expected that every pupil will give exactly the same answer. In No. 5, for instance, the cost of 99 yards is asked at $1.95 per yard. One pupil may consider 100 yards at $2, or $200; a second may keep the rate at $1.95, and say $195; a third might come still closer; each of such answers, however, should be accepted as an approximation.

1. What will be the cost of 39 pounds butter at 20¢ per pound?

Nearly 40 pounds at 204. The cost is nearly what? Solve.

2. A man has 4200 pounds of flour which he wishes to put into barrels containing 196 pounds each. About how many barrels will he need?

Each barrel contains nearly how many pounds? Solve.

3. A merchant bought a hogshead of molasses, containing 47 gallons, at 50 cents per gallon. About how much did it cost?

4. How many lots at $1975 each can be bought for $12,000?

5. Sold 3 pieces of cloth, 33 yards to the piece, at $1.95 per yard. Give the approximate amount of the bill.