bobdylan wrote:In the arithmetic sequence t1,t2, t3...tn, t1=23 and tn= t(n-1)-3 for each n>1. What's the value of n when tn= -4.
a)-1
b)7
c)10
d)14
e)20
Since tn= t(n-1)-3, the distance between one value and the next is 3.
Thus, the terms in the sequence are EVENLY SPACED, with an INTERVAL of 3 between successive values.
To count evenly spaced integers, use the following formula:
Number of integers = (biggest-smallest)/interval + 1
In the problem at hand:
Number of integers = (23-(-4))/3 + 1 = 10.
Since there are 10 terms, t(n) = -4 when n=10.
The correct answer is
C.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at
[email protected].
Student Review #1
Student Review #2
Student Review #3
