Question

Find the third proportional to 4 and 8

• A. 16
• B. 64
• C. 32
• D. 128

Answer 1

The correct option is A

16

Let the third proportional be $b$

Hence we have 4 : 8 :: 8 : $b$ are in proportion

Hence $\frac{4}{8}=\frac{8}{b}$

$4b$ = $8\times 8$

$b$ = $\frac{8\times 8}{4}$

= 16

Hence the third proportion to 4 and 8 is 16