Question

Find the fourth proportional of 8 , 488 and 13

• A. 13:14::39:42
• B. 11:1::33:3
• C. 16:15::48:45
• D. All of these

Answer 1

The correct option is A

13:14::39:42

Let $a$ be the fourth proportional

Hence we have 8 : 488 :: 13 : $a$

$8a$ = $488\times 13$ ( product of means is equal to product of extremes)

$a$ = $\frac{488\times 13}{8}$

= 793

Hence the fourth proportional is 793