Page:An introduction to linear drawing.djvu/96

 ﻿2. The circumference of a column is 10,5 what is its radius ? what its diameter ? Ans. R. 1,67 D.3,34.

3.	The circumference of a ship's mast is 136**', 15 what is its diameter ? Ans. 43,28 in.

4.	The circumference of a wheel is 48,75, what is its radius and diameter ? Ans. R. 7,75 D. 15,5.

SECTION II.

OF SURFACES.

Problem I. To find the surface of a parallelogram#

Rule. The surface of a parallelogram (fig. 16,) or rectangle (fig. 14,) is found by multiplying the base by the height. That of a square is found by multiplying one of the sides by itself.

Example 1. A rectangle has 2in-,24 for its base, 4ln-,31 for its height, what is its surface ?

2,24

4,31

224 67 2 * 896

9,6544 surface.

That is, 9 square inches, and 65 hundredths of a square inch.

2. A room is 154,6 inches long, and 75,3 wide, what is its surface or area ?

8