Question

Find the third proportion of 4 and 2.8

Answer 1

To find :

the third proportional of 4 and 2.8

Let's assume:

• the third proportional as 'c'
• the second proportional (2.8) as 'b'
• the first proportional (4) as 'a'

We know that :

if three numbers are in continued proportion

then,

a:b :: b:c

or, b² = ac

because, product of mean = product of extreme

Solution:

according to above law,

2.8² = 4(c)

$\implies \bold{ 7.84 =4c} \\ \implies \bold{c = \frac{7.84}{4} } \\ \implies \bold{ c = 1.96}$

hence, the third proportional = 1.96

hence, the required proportion =

4 : 2.8 :: 2.8 : 1.96