In the arithmetic sequence t1, t2, t3, ..., tn, ..., t1=23 and tn=t(n-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
OA: C
A -1
B 7
C 10
D 14
E 20
OA: C
For an AP
the nth term is given by an = a1+ (n-1) d
where a1- 1st term n->number of terms d-common difference
t1=23 t2 will be 23-3 = 20 so d=-3
Here we have a4(t4 same) is given , a1(or t1 the same thing), d->3 a
So using the formula
-4 = 23 + (n-1) -3
Solve for n; n=10
