Question

five numbers are in continued proportion the first number is 5 and last number is 80 then find the number

Answer 1

Continued proportion : Three numbers ‘a’, ‘b’ and ‘c’ are said to be continued proportion if a, b and c are in proportion.

Thus, if a, b and c are in continued-proportion, then

a,b,b,c are in proportion, that means

Product of extremes = Product of means

⇒ a x c = b x b

⇒ a x c = b 2

Continued-proportion is also known as mean proportional .

If ‘b’ is a mean proportional between a and c then b 2 = ac.

Examples :

1) Find the mean proportional between 9 and 25.

Solution :

Let x be the mean proportional between 9 and 25.

⇒ x 2 = 9 x 25

⇒ x 2 = 225

⇒ x = 15

Hence, the mean proportional between 9 and 25 is 15.