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why is B sufficient?

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Source: — Data Sufficiency |
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by bluementor » Tue May 05, 2009 3:30 am
In this sequance, t(n+1) = t(n)/2

So,

t2 = (1/2)*t1,
t3 = (1/2)*t2 = (1/4)*t1
and so on…

t5 = (1/2)*t4 = (1/2)*(1/2)*t3 = (1/2)*(1/2)*(1/2)*t2 = (1/2)*(1/2)*(1/2)*(1/2)*t1
t5 = (1/16)*t1

Statement 1: t3 = 1/4

t5 = (1/2)*(1/2)*t3
t5 = (1/2)*(1/2)*(1/4)
t5 = 1/16

Sufficient.

Statement 2: t1 - t5 = 15/16

t1 - (1/16)t1 = 15/16
t1*(1 - 1/16) = 15/16
t1*(15/16) = 15/16
t1 = 1

So t5 = (1/16)*t1 = 1/16. Sufficient.

Choose D.

-BM-
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