**MACHINE SHOP CALCULATION - OD1640 - LESSON 1/TASK 1**

EXAMPLE

Find the difference between 5/6 and 8/15.

The LCD is 30.

Change both

fractions to 30ths.

5/6 = 25/30

8/15 = 16/30

Subtract these fractions by subtracting their numerators, 25 - 16 = 9.

Place the 9 over the denominator 30 and the result is 9/30 = 3/10.

b.

*Subtracting Mixed Numbers*.

(1) *Rule 1*.

To subtract mixed numbers, subtract the fractional and the

whole parts separately.

Then add the remainder of the fractions to the

remainder of the whole numbers to get the answer in a mixed number.

EXAMPLE

From 27 5/6 take 14 5/8. Write it down as 27 5/6 - 14 1/8.

The LCD of 8

and 6 is 24. The subtraction then reads:

27 5/6

=

27 20/24

-14 1/8

=

-14 15/24

Subtract the numerators of the fractional part.

Then subtract the whole

numbers. Add these two results; the correct answer is 13 5/24.

(2) *Rule 2*. To subtract a fraction or mixed number from a whole number,

such as 17 - 9/11, or to subtract a fraction from a mixed number in which

the fraction of the minuend (the number from which another number is to be

taken), is less than the fraction of the subtrahend (the number to be taken

from the minuend), such as 12 5/8 - 7 7/8, borrow one from the whole number