next number of the sequence 4, 2, 1/2, -5/8, -47/32 ...... will be

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26 Mar 2012 1 addition 2 subtraction 3 multiplication 4 division

next number of the sequence
4, 2, 1/2, -5/8, -47/32 ...... will be

OPtion

1) -97/64
2) -99/64
3) -123/128
4) -149/128
5) -269/128
6) -327/128
7) -327/256
8) -149/256
9) -123/384
10) none of these

Solution

(4/4)*3-2+1 = 2
(2/4)*3-2+1 = 1/2
{(1/2)/4}*3-2+1 = -5/8
{(-5/8)/4}*3-2+1 = -47/32
{(-47/32)/4}*3-2+1 = -269/128

Correct Option: 5 Best Solution (8)

Balakrishnan M   12 years AGO

4(3/4)-1=2,
2(3/4)-1=1/2,
(1/2)*(3/4)-1=-5/8,
(-5/8)*(3/4)-1=-47/32,
(-47/32)*(3/4)-1=-269/128,
next number of the sequence
4, 2, 1/2, -5/8, -47/32 ......is -269/128.

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niru   12 years AGO

series goes like 3/2,9/8,27/32,81/128.......... so ans is (-47/32)-(81/128)=-269/128

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Sikandar chouhan   12 years AGO

multiply the sequence by 32.then the sequence will be 128,64,16,-20,-47... then take the differences bw them them 64,48,36,27 here 64 is the squae of 8 and 36 of 6 and the 2nd term is multiplication of both. by this approach we observe that 36 is square of 6 and 27 is multiplication of 6 and (9/2) so the diff sequence will be 64,48,36,-(27),-81/4 now add -81/4 into -47 and divide by 32

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arunraj   12 years AGO

Logic=> - 1/3 * [2^(2-2n) * (3*2^2n - 8*3^n)]

Sequence will be:
4, 2, 1/2, -5/8, -47/32, -269/128, -1319/512, -6005/2048, -26207/8192, -111389/32768, ......

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chiru   12 years AGO

from the sequence clearly we observe that it is in the following logic i.e.,
4,4-(3^0/2^-1),2-(3^1/2^1),(1/2)-(3^2/2^3),
(-5/8)-(3^3/2^5),(-47/32)-(3^4/2^7)[=-269/128]
hence option 5 is the reasonable one..and 20/3 is the one that present before 4..thank u..

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Shiv Kumar   12 years AGO

4, 2, 1/2, -5/8, -47/32
First Difference is
-2,-3/2,-9/8,-27/32 ---- 1

Next difference will be -81/128 ( difference is increment of 3/4 for the next number)

Next number in the sequence will be
(-81/128)+(-47/32)
=-269/128

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Viru Sihag   12 years AGO

First of all multiply the whole sequence by 32 and then find the difference between these and then u can easily find the next no. of this sequence.

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nithya   12 years AGO

4 - 2 =2
2 - 3/2 =1/2 ( each step *numerator by 3 and * denominator by 4 then subtract with previous no)
1/2 - 9/8 = -5/8
-5/8 - 27/32 = -47/32
-47/32 - 81/128 = -269/128

Like? Yes (1) | No (1)