Arithmetic Grade Five

Lesson Fifty-five: Decimal Multiplication and Parentheses


Remember that you do multiplication before addition or subtraction. Consider the following examples.

	.5 x .3 + .4 = .55

	.5 x (.3 + .4) = .35

	.4 - .2 x .3 = .34

	(.4 - .2) x .3 = .06
	
Why do the following two problems have the same answer?

	.4 x .3 + .3 = .42

	(.4 x .3) + .3 = .42

The reason that these two problems have the answer is that the parentheses are not necessary. We already do the multiplication first and so the parentheses don't change a thing.

Here's another example:


	.3 + .6 x .4 = .54

	(.3 + .6) x .4 = .36

Here the parentheses do make a difference.

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