Question

What is the sum of the series?

Answer 1

60

Explanation:

`\sum\limits_(i=1)^54i\to a_i=4i\\\\for\ i=1:\\\\a_1=4(1)=4\\\\for\ i=2:\\\\a_2=4(2)=8\\\\for\ i=3:\\\\a_3=4(3)=12\\\\for\ i=4:\\\\a_4=4(4)=16\\\\for\ i=5:\\\\a_5=4(5)=20\\\\\sum\limits_(i=1)^54i=4+8+12+16+20=60`