Arithmetic Grade Five

Lesson One Hundred and Twenty: Averages of Mixed Numbers

You will recall the method used to find the average of a group of whole numbers: 


	NUMBERS: 4, 7, 6, 3, 5.

	STEP ONE: Add the numbers.

		4 + 7 + 6 + 3 + 5 = 25

	STEP TWO: Divide the sum by the number of values.

		25 ÷ 5 = 5

	ANSWER: 5
Finding the average of a group of fractions is not much more difficult. 

	FRACTIONS: 2/3, 3/5, 1/3, 2/5, 1/4.

	STEP ONE: Add the fractions.

		2/3 + 3/5 + 1/3 + 2/5 + 1/4 =

		Find least common denominator: 60

		Convert fractions:

		  40/60 + 36/60 + 20/60 + 24/60 + 15/60 =

		Add fractions:

		  135/60

	STEP TWO: Divide by number of values.

		135/60 ÷ 5 =		(original problem)

		135/60 * 1/5 =		(flip and convert operator)

		135/300 		(multiply)

		9/20			(reduce)
Actually that's a lot of steps, but none of the steps is new.

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