Anindya Madhudor wrote:a(1), a(2),...., a(15)
In the sequence shown, a(n) = a(n-1) + k, where 2<=n<=15 and k is a nonzero constant. How many of the terms in the sequence are greater than 10?
1) a(1)=24
2) a(8)=10
.
Statement 1 is clearly insufficient.
Statement 2: a₈ = 10.
If k>0, then the sequence is INCREASING: each term in the sequence is GREATER than the preceding term.
In this case, a₉...a�₅ -- a total of 7 terms -- will be greater than 10.
If k<0, then the sequence is DECREASING: each term in the sequence is LESS than the preceding term.
In this case, a�...a₇ -- a total of 7 terms -- will be greater than 10.
In each case, the number of terms greater than 10 = 7.
SUFFICIENT.
The correct answer is
B.
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