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SAT Math: Arithemetic

The Number Line

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The letters a, b, c, and d represent numbers on the number line above.  Which of the following expressions has the greatest value?

A. a + b
B. c + d
C. a + d
D. c - b
E. a - b

Knowsys Method

Read the question carefully.  There are two important things to note about this question.  First, you know that the image is drawn to scale because you do not see any indication otherwise.  Second, the question asks you for the expression with the GREATEST value.  

Identify the bottom line.  Which expression has the greatest value?

Assess your options.  You could use the number line to solve this problem, or you could determine the value of each letter and solve the expressions mathematically.  The latter option is more concrete, so we will pursue that option.  

Attack the problem.  You can easily determine the number value of each letter if you note that the marks on the number line represent fourths.  Write down the value of each letter.

Screen Shot 2013-11-27 at 9.19.36 AM.jpg

Now simply plug these numbers into each of the expressions to determine which one has the greatest value.

Screen Shot 2013-11-27 at 9.19.45 AM.jpg

Choose the expression with the greatest value, which is answer choice B.

Loop Back.  Did you find the expression with the greatest value?  Yes.  

The correct answer is B.
This is a hard level question.

 

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