A right triangle ABC is shown below:A right triangle ABC with height AB labeled 4 units and base BC labeled 5 units is shown.The area of the triangle above will equal one half of a rectangle that is 5 units long and __ units wide. (Input only whole numbers, such as 8.)

The answer is:  "4" .
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Note:  The question asks for a whole number.

"The area of the triangle above will equal one half of a rectangle that is 5 units long and   4   units wide.  (Input only whole numbers, such as 8.).
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Note:  The diagram shows a "right triangle" ; which would be "one-half" of a rectangle, with units of "length" being "5 units" (as mentioned in this very question prompt;  and a width of "4" units (as shown in the diagram;  hence the answer is "4" units). 

Furthermore, the formula/equation for the area, "A" , of a triangle is: 


A = (1/2) * b * h ; 

that is: 

Area = (1/2) * (base length) * (perpendicular height).
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As such, the answer, "4" (units) makes sense.
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