The attendance for the first night of a play is 455. The attendance increases by 16 on each of the next 9 nights.
What is the total attendance for the 10 nights?
First night = 455
Last night = 455 + 9(16) = 599
Sum =
[ first night + last night ] * number of nights / 2 =
[ 455 + 599 ] * 10 / 2 =
1054 * 5 =
5270
+491 
