A whale goes on a feeding frenzy that lasts for 9 hours. For the first hour he catches and eats x kilos of plankton. In every hour after the first, it consumes 3 kilos of plankton more than it consumed in the previous hour. If by the end of the frenzy the whale will have consumed a whopping accumulated total 540 kilos of plankton, how many kilos did he consume on the sixth hour?
Answers.
A) 38	B) 47	C) 50	D) 53	E) 63
If you list the amount eaten each hour, you'll get an equally spaced list, increasing by 3 each hour. In any equally spaced list, the median equals the mean. Here, the mean is  540/9= 
<gadget id="calculator"> 540/9</gadget>
<output>60</output>
60, so the median is also 60, and that is the amount eaten in the 5th hour. We need to add 3 to find the total eaten in the next hour, so the answer is 63.   option 63.
<result>E</result>
A whale goes on a feeding frenzy that lasts for 9 hours. For the first hour he catches and eats x kilos of plankton. In every hour after the first, it consumes 3 kilos of plankton more than it consumed in the previous hour. If by the end of the frenzy the whale will have consumed a whopping accumulated total 540 kilos of plankton, how many kilos did he consume on the sixth hour?