Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 100)
100.
2 + 22 + 23 + ... + 29 = ?
Answer: Option
Explanation:
| This is a G.P. in which a = 2, r = | 22 | = 2 and n = 9. |
| 2 |
 Sn = |
a(rn - 1) | = | 2 x (29 - 1) | = 2 x (512 - 1) = 2 x 511 = 1022. |
| (r - 1) | (2 - 1) |
Discussion:
7 comments Page 1 of 1.
Darla said:
2 years ago
@Pawan.
An arithmetic sequence has a constant difference between each term- 2, 4, 6, 8, 10, 12.
Here, all are added by 2 whereas geometric sequence has a constant ratio ie, multiplier between each term- 2, 4, 8, 16, 32. Here, all are multiplied by 2.
An arithmetic sequence has a constant difference between each term- 2, 4, 6, 8, 10, 12.
Here, all are added by 2 whereas geometric sequence has a constant ratio ie, multiplier between each term- 2, 4, 8, 16, 32. Here, all are multiplied by 2.
Pawan said:
2 years ago
How can you say that it's GP? Explain please.
Maneesha said:
3 years ago
Geometric Progress.
DONKUPAR LYNNONG said:
3 years ago
What is the full form of G. P?
Mohit bansal said:
7 years ago
Any other method? Not by direct multiplying or gp, in search of any other method to this type of questions.
Pari said:
8 years ago
2+4+8+16+32+64+128+256+512 = 1022.
It's simple.
It's simple.
Nilesh said:
8 years ago
Help me please why (r-1) take?
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