Page 101 - New Medley 5 Semester 2

Let us check whether the given flags justify this condition.
Flag I Length = 30 cm,

Breadth = 20 cm

\ Length : Breadth = 30 : 20 = 3 : 2

Flag II Length = 120 cm,

Breadth = 80 cm

\ Length : Breadth = 120 : 80 = 3 : 2

Thus, we see that 30 : 20 and 120 : 80 are equivalent to 3 : 2.

i.e., 30 : 20 = 120 : 80

When two ratios are equal, they are said to be in a proportion. In other
words, two equivalent ratios form a proportion. Proportion is expressed
using the symbol ‘: :’ and it is read as ‘is the same as’.

Thus, the above equivalent ratios are expressed as 30 : 20 : : 120 : 80

and read as 30 is to 20 is the same as 120 is to 80.

Terms of a Proportion

In a proportion a : b : : c : d, there are four terms a, b, c and d. These

terms are respectively called first, second, third and fourth terms of the

proportion. Out of the four, first and fourth terms are called extreme
terms or extremes and second and third terms are called mean terms
or means.

Means

i.e., a : b : : c : d

Extremes
Relationship Between Means and Extremes of a Proportion

Consider the following proportions (a : b : : c : d)

I. 2 : 5 : : 10 : 25 II. 8 : 12 : : 6 : 9 III. 1 : 7 : : 21 : 147

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