# Aptitude - Ratio and Proportion - Discussion

Discussion Forum : Ratio and Proportion - General Questions (Q.No. 13)

13.

The fourth proportional to 5, 8, 15 is:

Answer: Option

Explanation:

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

Then, 5 : 8 : 15 : *x*

5*x* = (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.

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.

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.

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.

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?

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

(2)

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