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
in the minuend. Add this to the fraction, making it an improper fraction.
Then subtract.
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