# 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
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:
30 comments Page 1 of 3.

Rahul v said:   9 months ago
The number of proportional are only in even numbers that's why they are proportional.

Arijit said:   3 years ago
If a:b :: c:d then;
d = b*c/a (Formula),
Here, d is called the fourth proportion of a, b and c.

Meer showkat said:   3 years ago
If we have 3 or 5 numbers in a proportion, then how to find the last number?
(1)

Ramu Kanojiya said:   3 years ago
Thanks all.

Sandeep said:   3 years ago
5:8:15:x.
5/8=15/x.
When dividing 15 by 5, its come=3(upper parts are divided ).
Now multiply crossing,
x=24.

Bii said:   3 years ago
In that case 8/15 and 15/24 are not equal. The answer is 28.

Manish said:   3 years ago
Product of means = product of extremes.

Ajay Bhagat said:   4 years ago
5:8 = 15:x.

5/8 = 15/x.
5x = 15 * 8.
x = 90/5,
x =18.

Sk.Rahul Basha said:   4 years ago
4th proportion formula.
d = bc/a.

Here. a=5,b=8,c=15,
Now submit in formula.
d=8*15/5=24.

Jay said:   6 years ago
How to find fifth proportional?

Eg: Find the fifth proportional to 15, 18, 33, 51?
(2)