MACHINE SHOP CALCULATION - OD1640 - LESSON 2/TASK 2
Ratio and Proportion
. Ratio and proportion
for reducing the confusion
and minimizing the possibilities of error in working arithmetic problems. A
working knowledge of these methods makes it easier to solve many shop
problems. The language of ratio and proportion is mostly a sign language.
Letters and symbols are commonly used in place of long numbers and represent
unknown quantities and values.
(1) Ratio is the relation which one quantity bears to another quantity of
the same kind.
It is used extensively in shop work.
Shop drawings or
blueprints are generally drawn to scale. Scale means one figure is used to
represent another. Usually a small figure represents a larger figure. For
example, on a blueprint 1 inch might represent 1 foot.
(2) The two numbers used in the ratio are called the "terms" of the ratio.
The first number of a ratio is called the antecedent; the second number is
called the consequent. The consequent is the divisor. The colon (:) is the
sign of ratio and means "is to." Thus, 3 : 5 reads "3 is to 5." It is in
effect a dividing sign without the dividing (-) line.
all have the same meaning.
(3) The ratio of one number to another is really the quotient of the first
number divided by the second number.
Divide 8 by 2.
Thus, the ratio or value of 8 to 2
(4) The value of a ratio is not changed by either multiplying or dividing
both terms by the same number.