Find out the 10th term of a geometric progression and the sum if a1 = 35 and the common ratio (C.R) r = 2
Solution:
Use the formula an=a1×rn−1an=a1×rn−1 that gives the nth term to find a10a10 as follows
a6=35×(2)10−1a6=35×(2)10−1
= 35 * (2)9
= 35 * 512
After simplifying this, we get
= 17920
The 10th term of a geometric sequence is 17920
Series of the sequence: snsn = a1(1−rn)1−ra1(1−rn)1−r
s10s10 = 35(1−210)1−235(1−210)1−2
= 35(−1023)−135(−1023)−1
After simplify this, we get
s10=35805s10=35805
The above examples are helpful to learn geometric progression sum formula.