In the arithmetic sequence t1, t2, t3......tn....., t1 = 23... tn = tn-1 - 3 for each n>1. What is the value of n when tn= -4
A) -1
B) 7
C) 10
D) 14
E) 20
Can someone please explain their answer as well, the correct answer is down below
The answer is C
GMAT PREP (Arithmetic Sequence)
This topic has expert replies
We know that tn=(tn-1)-3, so the sequence is with arithmetic progression with tolerance: d = -3.
We have tn=t1+(n-1)*d, where t1=23, tn=-4 and d=-3, so we can solve the equation and find n.
-4=23-3*(n-1) =>n=10
We have tn=t1+(n-1)*d, where t1=23, tn=-4 and d=-3, so we can solve the equation and find n.
-4=23-3*(n-1) =>n=10
Yiliang