penters use a steel instrument called a square or T square, depending on whether its shape is that of the letter L or T. T CARPENTER'S SQUARE T SQUARE 8. (a) At a quarter of nine o'clock the hands are almost together. At 9 o'clock they form a right angle. In that fifteen minutes many different sized angles were formed, but all were less than a right angle. (b) Any angle whose size is less than a right angle is an acute angle. (c) Acute means sharp. (d) Draw an acute angle and see why it is properly named a "sharp" angle. RIGHT ANGLES ACUTE ANGLES OBTUSE ANGLES 9. (a) What is the size of the angle made by the hands of a clock at 9 o'clock? (b) At 9.15 it is almost but not quite a straight angle. (c) In that fifteen minutes many different sized angles were formed, but all were greater than a right angle and less than a straight angle. (d) Any angle that is greater than a right angle and less than a straight angle is an obtuse angle. (e) Obtuse means blunt. (f) Draw an obtuse angle and see why it is properly named a "blunt" angle. 10. (a) A carpenter tests his squares, that is, he sees whether they are true right angles or not, by placing two of them together on a straight (b) If the two edges exactly fit when thus placed, the 11. What kind of angle do the hands of a clock make at 3 o'clock? 12. Do they make the same kind at a quarter past 12? 13. At what times do they make right angles? 14. Do they make a straight angle at 12.30? 15. What kind of angle is made by the hands of a clock at 3.30, 3.35, 1.00, 1.30, 4.30, 8.00, 8.55, 8.40 o'clock? 1. (a) How many sides has a square? (b) Are all of the sides of a square equal? (d) Are all of the angles right angles? (e) Are all of these features necessary for a square? (f) Name all the necessary features of a square. 2. (a) Try making four-sided figures with only two of the other features, as given in (b), (c), and (d). (b) Make a four-sided figure which has only the feature (c). 3. (a) Which features are found and which are lacking in the following figures? (b) All of these figures are parallelograms because each has two pairs of parallel sides. (c) Parallelogram means parallel drawing. (d) The sign for parallelogram is. For the plural it is S. (e) Fill in these blanks to make a correct definition: A parallelogram is a figure inclosed by pairs of lines. (f) Is a square a parallelogram? (g) Is every square a rectangle? (h) Is every rectangle a square? (i) We always give the special name of square, rectangle, or rhombus to each of the particular kinds of parallelograms, but seldom use the name rhomboid. When we speak of a parallelogram we mean the general form or rhomboid. 4. (a) How many objects can you find having these shapes? (b) What is the shape of your schoolroom? of your school yard? of the pages of your book? of the door? 5. Below is a map of a section of a city. What are the shapes of the various city blocks? PARK C. MEASUREMENT OF AREA I. Area of Squares and Rectangles 1. On squared paper draw a picture of one face of a cube whose edge is one inch. This picture is called a square inch and is used to measure surface or area. (If metric units are desired, do the same with one centimeter.) 2. Draw a square whose edge is 2 inches. Count the number of square inches in it. This number is called the measure of the area or simply the area of the square. 3. Draw squares with different edges and count the square units in area. 4. By measuring one edge of a square, how may yo find the number of square units in its area? 5. On squared paper, draw several rectangles and cour the square units in their areas. E F Area of rectangle D = 4.3 or 12.1 sq. in. = 12 sq. in. 6. (a) Thus we find that the area or surface of a rectangle or of a square equals the length times the width. (b) In this statement let the first letters of the main words be used in their places. Then we have |