Arithmetic Grade Six

Lesson One Hundred Thirty-seven: Money Stack

Often test questions are designed to include distracting information which may mislead you. Word problems are likely places to hold distracting information. Consider the following example: 

	Waldo must wash 7 cars and 20 bikes. He gets paid $5 for
	each car he washes and $2 for each bike he washes. It is 
	105 degrees outside at 1:30 and Waldo would like to wait until it
	is a bit cooler to wash the cars and the bikes. So, he waits
	3 hours and 15 minutes, when the temperature has dropped by 15
	degrees, to start working.  [INSERT QUESTION HERE.]
The word problem up to this point presents lots of information and it will be up to us to decide which information will help us to answer the question. Here are four possible questions that could be asked at the end of this problem: 

	1) How much money will Waldo be paid for washing the cars?

	2) What time is it when Waldo starts washing cars and bikes?

	3) What is the temperature when Waldo starts working?

	4) How much money will Waldo be paid for washing the bikes?
What information we use to solve the problem depends on which question is asked. Let's say that question two is the one we are asked. This will make the number of cars and bikes, the amount he's getting paid, and the temperature all extraneous to the solution of the problem. In fact the only information we care about is the time at the beginning of the problem and the amount of time that he waits: 

   TIME AT BEGINNING OF PROBLEM:	1:30
   TIME WALDO WAITS:			3:15
   1:30 + 3:15 =			4:45

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