Feet can be changed to inches by multiplying the number of feet by 12 (the number of inches in a foot). Computing Pipe Offsets The illustration in Figure 4-9 presents a typical pipe offset problem. Two parallel pipes must be joined by a short length of pipe running at a Converting Feet to Inches and Inches to Feet It is often necessary to change dimensions given in inches to equal dimensions in feet and inches. Since there are 12 inches in a foot, this is done by dividing dimensions given in inches by 12, Figure 4-8. 1 2 3 4 1 2 3 4 5 6 53⁄4″ – 41⁄4″ = ______ 41⁄4″ 53⁄4″ Subtracting the numerators of the fractions produces the following results: 53⁄4″ – 41⁄4″ = ______″4⁄2 Subtracting the whole numbers gives: 53⁄4″ – 41⁄4″ = 12⁄4″ Now, 2⁄4″ can be written in a simpler, reduced form: 53⁄4″ – 41⁄4″ = 11⁄2″ Goodheart-Willcox Publisher Figure 4-5. Dimensions can be subtracted using the same methods shown in Figure 4-4. 1 2 3 4 1 2 3 4 5 6 61⁄2″ – 43⁄16″ = ______ 61⁄2″ 43⁄16″ When the denominators of the fractions are unequal, the fractions must be changed to equal fractions having common (equal) denominators. From Figure 4-1, it can be seen that 1⁄2″ = 8⁄16″. Therefore, the above problem can be written as: 68⁄16″ – 43⁄16″ = ______ Subtracting the fractions produces the following results: 68⁄16″ – 43⁄16″ = ______″16⁄5 Subtracting the whole numbers completes the problem: 68⁄16″ – 43⁄16″ = 25⁄16″ Goodheart-Willcox Publisher Figure 4-6. Method of subtracting dimensions given in fractions of an inch and having unequal denominators. 74 Section 1 Introduction to Plumbing Copyright Goodheart-Willcox Co., Inc.