VII. MEASUREMENTS LINEAR MEASURES Here is a picture of a splint 1 inch long: 1. About how many inches long is your book? 2. Make an inch splint, and with it measure the length and width of this page. 3. With a foot rule, measure the length and width of your desk. 4. With a yardstick, measure the length and width of the schoolroom. 5. Name something that is usually measured by the inch; by the foot; by the yard; by the mile. 13. How much will 7 ft. 9 in. of wire cost at 8¢ a foot? 14. How much will 5 yd. 2 ft. of cloth cost at 9f a yard? 186 How many inches are there in 25 yd. 2 ft. 7 in.? 16. How much will it cost to repair a road of a mile long at 9 a yard? /. Which of these figures is a square? a rectangle? 2. How many sides has each? Are all the sides of the rectangle equal? about the sides of the square? How In a square or in a rectangle the sides that meet are said to be perpendicular to each other. The sides that never meet C ONE SQUARE INCH are said to be parallel to each other. A surface is that which, like this page, E G D has length and width. Surfaces are measured by squares, so surface measures are called square measures. Copy and memorize : 144 square inches (sq. in.) = 1 square foot (sq. ft.). 9 square feet 4840 square yards 640 acres Let the pupil take a foot rule and some paper, and lay off and cut out squares of different sizes. What is the surface of a rectangle which is 5 inches long and 3 inches wide? The length and width are expressed in inches, so one square inch is the square unit (unit of surface) used as a measure. Since the rectangle is 5 inches long, in one row there are 5 x 1 sq. in. 5 sq. in., and since it is 3 inches wide, there are three rows. 3 x 5 sq. in. 15 sq. in. What is the surface of a rectangle 4 ft. long and 2 ft. wide? The length and width are expressed in feet, so one square foot is the unit of surface used as a measure. Since the rectangle is 4 ft. long, in one row there are 4 × 1 sq. ft. = 4 sq. ft., and since it is 2 ft. wide, there are 2 rows. 2 x 4 sq. ft. = 8 sq. ft. What is the surface of a rectangle 7 yd. long and 4 yd. wide? 7 x 4 x 1 sq. yd. = 28 sq. yd. What is the surface of a rectangle 2 ft. long and 3 in. wide? The length is expressed in feet, and the width in inches. be changed to like units. They must Find the surface of each rectangle whose width and length Try to give a rule for finding the surface or area of a rectangle. Compare your rule with the following: To find the area of a rectangle: Multiply its unit of surface by the product of the numbers showing its length and breadth. NOTE. Dimensions must always be expressed in, or changed to, like units. 1. How many square feet are there in the surface of a floor 20 ft. long and 14 ft. wide? 2. How many acres are there in a rectangular garden 110 yd. long and 88 yd. wide? 3. I have a plot of ground 42 ft. long and 15 ft. wide. How many square yards are there in its surface? 4. How much will it cost to floor a room 21 ft. long and 15 ft. wide, at 25 a square yard? |