1. If four quantities are in
proportion, then Product of
Means = Product of Extremes.
In the proportion a:b::c:d, we
have bc = ad
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2. If a:b::c:x, x is called the fourth
proportional of a, b, c.
a/b = c/x or, x = bc/a.
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3. If two numbers are in a:b ratio
and the sum of these numbers is
x, then numbers will be ax/ (a+b)
and bx/(a+b) respectively
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4. If three numbers are in the ratio
a:b:c and the sum of these
numbers is x, then these
numbers will be ax/(a+b+c) ,
bx/(a+b+c) and cx/(a+b+c)
respectively
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5. The ratio of two numbers is a : b.
If n is added to each of these
numbers, the ratio becomes c :
d. The two numbers will be given
as an(c-d)/(ad-bc) and bn(cd)/(
ad-bc) respectively
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6. The ratio of two numbers is a : b.
If n is subtracted from each of
these numbers, the ratio
becomes c : d. The two numbers
are given as an(d-c)/(ad-bc) and
bn(d-c)/(ad- bc) respectively
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7. If the ratio of two numbers is a: b,
then the numbers that should be
added to each of the numbers in
order to make this ratio c:d is
given by (ad-bc)/(c-d)
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8. If the ratio of two numbers is a:b,
then the number that should be
subtracted from each of the
numbers in order to make this
ratio c:d is given by (bc-ad)/(c-d)
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By - ExamAddaa Team
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