Aptitude - Ratio and Proportion - Discussion

Discussion Forum : Ratio and Proportion - General Questions (Q.No. 13)
13.
The fourth proportional to 5, 8, 15 is:
18
24
19
20
Answer: Option
Explanation:

Let the fourth proportional to 5, 8, 15 be x.

Then, 5 : 8 : 15 : x

5x = (8 x 15)

x = (8 x 15) = 24.
5

Discussion:
35 comments Page 4 of 4.

Sumitra said:   1 decade ago
It should be like this 5:8::15:x.

Then 5/8 = 15/x.

x = 15*8/5.
x = 24.

Isaacs nyondo said:   1 decade ago
It is really supposed to be.

5:8 = 15:x.

It means that they are terms of a sequence.

Then:

5/8 =15/x.

x = 15*8/5.

x = 24.

Main said:   1 decade ago
It should be 8x15 = 90.

5 then the answer is 18 because 90/5 = 18.

Sasulya said:   10 years ago
Just see diff. between 3 numbers and all are odd.

5 and 8 = 3 odd number.

8 and 15 = 7 odd number.

Then next odd num after 7 is 9.

Ramesh said:   10 years ago
They asked. How 5th proportional?


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