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
5x = (8 x 15)
| x = | (8 x 15) | = 24. |
| 5 |
Discussion:
34 comments Page 1 of 4.
Shipra said:
1 decade ago
Hello guys!
Its given,
5:8:15:x.
Where we take x as constant.
Now,
5/8 = 15/x.
=> 5 = (15*8)/x.
On cross multiplication we get,
x = (15*8)/5.
x = 3*8.
x = 24.
Its given,
5:8:15:x.
Where we take x as constant.
Now,
5/8 = 15/x.
=> 5 = (15*8)/x.
On cross multiplication we get,
x = (15*8)/5.
x = 3*8.
x = 24.
Akshay said:
9 years ago
@All.
There is no any formula they just use a simple logic of a/b/c/d i.e. (a/b) = (c/d) if we pass this term in side the equal to sign i.e.(a*d) = (b*c).
There is no any formula they just use a simple logic of a/b/c/d i.e. (a/b) = (c/d) if we pass this term in side the equal to sign i.e.(a*d) = (b*c).
(1)
Sasulya said:
9 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.
5 and 8 = 3 odd number.
8 and 15 = 7 odd number.
Then next odd num after 7 is 9.
Azeem said:
1 decade ago
Assume a=5, b=8, c=15.
We all know the ad = bc.
a = bc/d, b = ad/c, c = ad/b.
Simillarly d = bc/a.
So 8*15/5 => 120/5 = 24.
We all know the ad = bc.
a = bc/d, b = ad/c, c = ad/b.
Simillarly d = bc/a.
So 8*15/5 => 120/5 = 24.
Hanson said:
1 decade ago
Better still:
It will be split this way: 5:8=> 15:x.
Hence, the common factor is 15/5 = 3.
Thus, x/8 = 3.
x= 8*3 =24.
It will be split this way: 5:8=> 15:x.
Hence, the common factor is 15/5 = 3.
Thus, x/8 = 3.
x= 8*3 =24.
Isaacs nyondo said:
10 years 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.
5:8 = 15:x.
It means that they are terms of a sequence.
Then:
5/8 =15/x.
x = 15*8/5.
x = 24.
Sai said:
1 decade ago
Formula must be used compulsory ? we can assume it as in series form as 5, 15, 25, 35.... In same manner 8, 18, 28......
Pranav said:
1 year ago
Here is the solution
Let's write 5, 8, 15, X.
= (5/8) : (15/x),
= 15/x * 8/5,
Then x.= 3*8.
So, the Answer = 24.
Let's write 5, 8, 15, X.
= (5/8) : (15/x),
= 15/x * 8/5,
Then x.= 3*8.
So, the Answer = 24.
(5)
Shrishti said:
1 decade ago
This is solved by proportional formula such as a:b :: c:d
Formula: a*d=b*c (as said find fourth proportional).
Formula: a*d=b*c (as said find fourth proportional).
Manik said:
1 decade ago
Is this formula applicable for such other problems? What abt the formula of fifth, sixth or higher proportional?
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