Verbal Reasoning - Series Completion - Discussion
Discussion Forum : Series Completion - Section 1 (Q.No. 4)
Directions to Solve
Choose the correct alternative that will continue the same pattern and replace the question mark in the given series.
4.
In the series 2, 6, 18, 54, ...... what will be the 8th term ?
Answer: Option
Explanation:
Clearly, 2 x 3 = 6, 6 x 3 = 18, 18 x 3 = 54,.....
So, the series is a G.P. in which a = 2, r = 3.
Therefore 8th term = ar8-1 = ar7 = 2 x 37 = (2 x 2187) = 4374.
Discussion:
27 comments Page 2 of 3.
Sameer said:
1 decade ago
@Kanna.
Why we need to multiply with 3 With Given Numbers?
Why we need to multiply with 3 With Given Numbers?
Manjot singh said:
1 decade ago
2*3 = 6.
6*3 = 18.
18*3 = 54.
54*3 = 162.
162*3 = 486.
486*3 = 1458.
1458*3 = 4374.
6*3 = 18.
18*3 = 54.
54*3 = 162.
162*3 = 486.
486*3 = 1458.
1458*3 = 4374.
Sangeeta said:
1 decade ago
This series is in geometric progression:
So 8th term is = 2*3^(8-1).
= 2*3^(7).
= 2*3^(4+3).
= 2*[3^4*3^3].
= 2*[81*27].
= 2*2187.
= 4374.
So 8th term is = 2*3^(8-1).
= 2*3^(7).
= 2*3^(4+3).
= 2*[3^4*3^3].
= 2*[81*27].
= 2*2187.
= 4374.
Chiran said:
1 decade ago
What is the meaning of a and r please explain me?
Kanhay said:
1 decade ago
A means first term and are means common ratio.
(1)
Upender Singh Rajput said:
1 decade ago
Solving with GP. (Geometrical Progression) find 8th term.
Now Series is 2 6 18 54.....8th term.
So a =2, r=6\2=3, T8=2(3)7, T8 = 4374.
Now Series is 2 6 18 54.....8th term.
So a =2, r=6\2=3, T8=2(3)7, T8 = 4374.
Nrusingha acharya said:
10 years ago
An other method: 2.
6*3^0.
6*3^1.
6*3^2.
6*3^3.
6*3^4.
6*3^5.
6*3^6,
Only calculate the 8th one not all and get the result.
6*3^0.
6*3^1.
6*3^2.
6*3^3.
6*3^4.
6*3^5.
6*3^6,
Only calculate the 8th one not all and get the result.
Sameer said:
10 years ago
Why ^7 instead ^8 because there find out 8th place?
(1)
Nigerian boy said:
10 years ago
@Sameer.
From the formula T8 = ar (power N-1).
N stands for Number of terms you are looking for so all you need do is know that you have to subtract 1 from the number of terms.
Eg. 1. When the number of terms in question is 9 then the formula becomes T9 = ar9-1.
2. When it is 5 the formula becomes T5 = ar5-1.
From the formula T8 = ar (power N-1).
N stands for Number of terms you are looking for so all you need do is know that you have to subtract 1 from the number of terms.
Eg. 1. When the number of terms in question is 9 then the formula becomes T9 = ar9-1.
2. When it is 5 the formula becomes T5 = ar5-1.
(1)
Vaishnavi said:
9 years ago
Yes, using formula is also the correct method.
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