IMO D.
The values of the sequence are 2,3,5,10,20,40,80 ....
If we look at the pattern we can tell that for n > 3 all the numbers have 2 and 5 as factors
S4 = 10 = 2 x 5
S5 = 20 = 2^2 x 5
S6 = 40 = 2^3 x 5
Sn = 2^(n-3) x 5
The 30th term is 2 ^(27) x 5 and the 25th is 2 ^(22) x 5; therefore the ratio is 2 ^(27) x 5 / 2 ^(22) x 5 = 2 ^ 5 = 32
Sequences
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mikeCoolBoy
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mikeCoolBoy
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Sure you just have to take a look at the terms of the sequence. As I wrote.
S4 = 2 x 5
S5 = 2 ^ 2 x 5
S6 = 2 ^ 3 x 5
so Sn = 2 ^(y) x 5 and we have to calculate y according to n.
When n = 4 y = 1
when n = 5 y =2
so you can see that n - y = 3 and therefore y = n -3
I'm really bad at explaining things, maybe someone has another solution more clear.
S4 = 2 x 5
S5 = 2 ^ 2 x 5
S6 = 2 ^ 3 x 5
so Sn = 2 ^(y) x 5 and we have to calculate y according to n.
When n = 4 y = 1
when n = 5 y =2
so you can see that n - y = 3 and therefore y = n -3
I'm really bad at explaining things, maybe someone has another solution more clear.
I chose D as well...
I solved it like this...
I knew the sequence up the 10th value was:
2, 3, 5, 10, 20, 40, 80, 160, 320, 640...
The ratio for the sequence is going to stay the same thoughout between n and n+5 for n >= 3.
SO
I just selected to find the ratio between the 10th integer and the 5th.
With that you get 640/20, which equals 32/1.
I solved it like this...
I knew the sequence up the 10th value was:
2, 3, 5, 10, 20, 40, 80, 160, 320, 640...
The ratio for the sequence is going to stay the same thoughout between n and n+5 for n >= 3.
SO
I just selected to find the ratio between the 10th integer and the 5th.
With that you get 640/20, which equals 32/1.
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dumb.doofus
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Brilliant man!!! nice logic..cata1yst wrote:I chose D as well...
I solved it like this...
I knew the sequence up the 10th value was:
2, 3, 5, 10, 20, 40, 80, 160, 320, 640...
The ratio for the sequence is going to stay the same thoughout between n and n+5 for n >= 3.
SO
I just selected to find the ratio between the 10th integer and the 5th.
With that you get 640/20, which equals 32/1.
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