find the 15th term in the geometric sequence below. 20,10,5,2.5,...

Question

anonymous · Answer

to find the nth of a general term of a geometric sequence, 
$$a _{n}=a _{1} \times r ^{n-1}$$

anonymous · Answer

$$a = 20 , r = 10/20 = 1/2 $$
T15 = a . r ^ 14
       = 20 x ( 1/2 ) ^ 14
        = ..... !

anonymous · Answer

a(n) = the nth term of the series
a(10=the 1st term of the series
r=common ratio
n=nth term

anonymous · Answer

@kausarsalley  how can the 15th term be greater than 20 if the sequence is 
20 , 10 , 2.5 ... ( notice it is decreasing ) how can you obtain 327680 ? o.O

anonymous · Answer

so in this case, since you are finding the nth term,
$$a _{n}= 20 \times 0.5^{15-1}$$
$$a _{n}=0.00122.....$$

anonymous · Answer

@antoni7    i made a mistake......i have made the correction.....
anyway thanks for letting me know.....

anonymous · Answer

no problem.. we are all learners here