Question 144243
Let's put this in symbols:

{{{sum( (-1/6)^k*42, k=0, k=9 )}}}

The sum is simplified by using:

{{{a(1-r^(n+1))/(1-r)}}}
Where a= first term, r= common ratio, n= top kth number. So,
a=42; r=(-1/6); n=9.


{{{42(1-(-1/6)^(9+1))/(1-(-1/6))}}}
=
{{{(6/7)42(1-(-1/6)^(10)))}}}
=
{{{36(1-(-1/6)^(10)))}}}
Use a calculator for the answer of:
=35.9999994; c.