Answer:
[tex]S_{n}=15[/tex]
Step-by-step explanation:
from the question given i can infer that it is a geometric sequence. this question is asking for the sum of the first four pennies in on the row
therefore using the formula for the sum of a geometric sequence which is
[tex]S_{n} =\frac{a(r^{n}-1) }{r-1}[/tex]
so substituting the values of a, r and n into the the equation above
[tex]S_{4}=\frac{1(2^{4}-1) }{2-1} \\S_{4} =\frac{1(16-1)}{1} \\\\\S_{4} =1(15)\\S_{4} =15[/tex]
