Page:An introduction to linear drawing.djvu/95

 ﻿2. The width of a basin is how long must a string be to reach round it ?

5,5 3

16,5

A seventh of 5,5. . 0,786

Length of thestring,. . 17,286 the circumference.

3.	The diameter of a circle is 4,45, what is the cir- cumference? Ans. 13,98 inches.

4.	The diameter of a ring is 1,5, what is the circum- ference ? Ans. 4,7 inches.

5.	The diameter is 4,17, what is the circumference ? Ans. 13,1 in.

Problem III. The circumference being known, to find the radius.

Rule. Multiply the circumference by 0,159 and you will have the radius.

Example 1. To find the thickness of a column, its circumference has been measured with a string and found to be 12,542—required the radius.

12,542 0,159

0 112878 62710 12542

1,994178 radius.

If 1,994 thousandths be the radius or half diameter, 3,988 will be the whole diameter of the column. Six figures are separated, because there are three in the multiplier, and 3 in the multiplicand. The three right hand decimals are unimportant.