Tough and Tricky questions: Word Problems.
A salesman's income consists of commission and base salary. His weekly income totals over the past 7 weeks have been $406, $413, $420, $436, $395, $410, $360. What must his average (arithmetic mean) income over the next two weeks be to increase his average weekly income to $500 over the 9-week period?
Choices
A) $570	B) $790	C) $630	D) $830	E) $715
OFFICIAL SOLUTION:   (D) First, we need to add up the wages over the past 7 weeks: $406 + $413 + $420 + $436 + $395 + $410 + $360 = $2840.   To average $500 over 9 weeks, the salesman would need to earn: $500 × 9 406 +  413 +  420 +  436 +  395 +  410 +  360= 
<gadget id="calculator">406 +  413 +  420 +  436 +  395 +  410 +  360</gadget>
<output>2_840</output>
$2840.   To average $500 over 9 weeks, the salesman would need to earn: $500 × 9= $4500.   Subtract $2840 from $4500 to determine how much he would need to earn, in total, over the next 2 weeks to average $500 for the 9 weeks: $4500 – $2840 = $1660.   Dividing $1660 by 2 will give us the amount he needs to earn on average over the next 2 weeks: $1660/2= 
<gadget id="calculator">1660/2</gadget>
<output>830</output>
$830.   The correct answer is choice ($830).
<result>D</result>
Tough and Tricky questions: Word Problems.
A salesman's income consists of commission and base salary. His weekly income totals over the past 7 weeks have been $406, $413, $420, $436, $395, $410, $360. What must his average (arithmetic mean) income over the next two weeks be to increase his average weekly income to $500 over the 9-week period?