in the first choice, we are given the first term. we dont have any value for k.
so insuff... we cant tell if k is positive or negative. eliminate a,d
from 2.) if u carefully check its the middle term of the 15 terms. the no of terms is odd. so, in any case there are seven terms below a8 and seven terms above a8. so it is suff to answer the question. hence B.
hope it helps..
DS Seq
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logitech
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jimmiejaz - great work.moneyman wrote:I dont understand how B is sufficient
Moneyman,
You can see that:
a2 = a1 + k
a3= a2 +k or, (a1+k) + k
which is a1+2k
in other words this is how your series look like
a1, a1+k, a1+2k, ......, a1+14k
and remember we have 15 terms in this series
a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 a11 a12 a13 a14 a15
and a8 is in the middle
but the question or the answers have no information about what k is
but if we know that a8 = 10, either k is negative or positive, we will have 7 numbers greater than 10.
a1 a2 a3 a4 a5 a6 a7
or
a9 a10 a11 a12 a13 a14 a15
LGTCH
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jimmiejaz
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yes ... you got it right mate!!!!moneyman wrote:Thanks jimmiejaz..It looks like an evenly spaced set then isnt the middle number the average as well?
in an evenly spaced set or a set of consecutive integers, the mean is the median.
Hope it helps.
