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 decrease his average weekly income to $400 over the 9-week period?  Options:
A) $360 B) $380 C) $430 D) $290 E) $520
OFFICIAL SOLUTION:   (B) First, we need to add up the wages over the past 7 weeks: $406 + $413 + $420 + $436 + $395 + $410 + $360 = $2840.   To average $400 over 9 weeks, the salesman would need to earn: $400 × 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 $400 over 9 weeks, the salesman would need to earn: $400 × 9= $3600.   Subtract $2840 from $3600 to determine how much he would need to earn, in total, over the next 2 weeks to average $400 for the 9 weeks: $3600 – $2840 = $760.   Dividing $760 by 2 will give us the amount he needs to earn on average over the next 2 weeks: $760/2= 
<gadget id="calculator">760/2</gadget>
<output>380</output>
$380.   The correct answer is choice ($380).
<result>B</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 decrease his average weekly income to $400 over the 9-week period?