Arun spent six lucky days in Las Vegas. On his first day he won a net amount of only $20, but on each of the following days, the daily net amount he won grew by d dollars. If Arun won a total net amount of $1620 during his stay in Las Vegas, how much did he win on the last day?
Answers.
A) 330
B) 500
C) 520
D) 540
E) 620
I drew a diagram:   1 - $20   2 -   3 -   4 - $320   5 -   6 -   Total: $1,620   Between 1 and 6 are 5 days where he won $1,600. This means he averaged $320 per day (1600/5). You can put $320 by 4 because it's the middle number. Now you just find the two points betwenn $20 and $320 (320-20 = 300 / 3= 
<gadget id="calculator">300 / 3</gadget>
<output>100</output>
100). So each day, he earned $100 more. This means on day 6, Arun earned$520. Answer choice 520.
<result>C</result>
Arun spent six lucky days in Las Vegas. On his first day he won a net amount of only $20, but on each of the following days, the daily net amount he won grew by d dollars. If Arun won a total net amount of $1620 during his stay in Las Vegas, how much did he win on the last day?