Notes of Lessons: Arithmetic, Class III

Notes of Lessons: Arithmetic, Class III

[We have thought that it might be of use to our readers (in their own families) to publish from month to month during the current year, Notes of Lessons prepared by students of the House of Education for the pupils of the Practising School. We should like to say, however, that such a Lesson is never given as a tour de force, but is always an illustration or an expansion of some part of the children’s regular studies (in the Parents’ Review School), some passage in one or other of their school books.—Ed.]

Group: Mathematics • Class III • Time: 30 minutes

By B. M. Goode
The Parents’ Review, 1904, pp. 716-717 

Objects

I. To give additional help in questions of area by teaching the children how to find the amount of material required for covering a rectangular surface, the width of the material being given.

II. To encourage accuracy by methodical working and briskness of statement and calculation.

III. To make the children use their common sense by giving approximate answers.

Lesson

Step I.—Recapitulation. Ask what it is necessary to know in order to find the area of rectangular surfaces. Take as examples the floor of a room, the walls of a room and the sides of a tank. Give a few oral examples.

Step II.—Ask what is the practical use of knowing the area of such surfaces, and show that since paper and carpet, etc., are not sold in pieces to fit any surfaces, but in narrow widths by the yard, some calculation is necessary to find the required amount.

Step III.—Draw a diagram representing a rectangular surface, 12 in. by 6 in., covered with dominoes, 1 in. by 2 in. Draw from them the method of finding out the number of dominoes occupying the surface, by finding the area of one domino, and dividing the whole area by the area of one domino. Show that in the same way, if we find the area of one yard of carpet, divide it into the total area to be covered, the number of yards can be ascertained.

Step IV.—Draw from them that it is necessary to know the width of the carpet before the area of a yard can be ascertained. Point out that what we talk of as a yard of carpet is not a yard square. Give oral examples to find out the area of a yard of carpet, paper, etc.

Step V.—After recapitulating the steps, work an example on the board; pointing out the method of stating it.

Example.—How much drugget 5 1⁄4 ft. wide is necessary to cover a floor 22 ft. 6 in. by 16 ft. 4 in.?

Area of floor = 22 1⁄2 ft. x 16 1⁄3 ft.

= 15⁄2 x 49

= 735⁄2 square feet.

  Area of 1 yd. of drugget = 5 1⁄4 ft. x 3 ft.

= 21⁄4 x 3

= 63⁄4 square feet.

      Number of yards required = 735⁄2 ÷ 63⁄4

= 35 x 2⁄3

= 23 1⁄3 yards.

Let each child work an example on the board, if time permits.