You put 500 pieces of paper in a copy machine. When you check back 6 days later, there are only 320 pieces left. How many pieces of paper are being used each day?

1 Answer
Oct 30, 2016

The mean usage over 6 days is 30 per day


Realistically you do not know. One day may use more than another. For example: they may all have been used on day 5 and none on all the other days.

The mean (average) use is all you can determine.

#color(blue)("Determine total count of used pieces of paper")#

#cancel(5)^4 cancel(0)^10 0#
#ul(3color(white)(..)2color(white)(..)0)" "larr" subtract"#
#1color(white)(..)8color(white)(..)0 " "larr" total used"#

#color(blue)("Determine the mean use per day")#

Using ratio in fraction format

#" "("Paper count")/("day count")->180/6#

This is for 6 days but we need the count for 1 day

With ratio what you do to the bottom you also do to the top for multiply or divide. This maintains the correct proportions.

#" "("Paper count")/("day count")->(180-:6)/(6-:6) = 30/1#

So the #ul("mean")# usage over 6 days is 30 for each day