Arithmetic Grade Six

Lesson Seventy: Decimal Multiplication

The steps you take to solve a decimal multiplication problem like the one shown below are the same as with a regular multiplication problem except that you have to remember to place the decimal in the answer. 

	   5.12
	 x  .24
	--------
	   2048		<--- partial product one
	  1024		<--- partial product two
	--------
	 1.2288		<--- final product with decimal point
In general you just count up the decimal places in the problem and make sure that you put that many decimal places in your answer. In the last example both 5.12 and .24 have two decimal places each for a total of four decimal places. So, the answer is 1.2288 because the answer will also have four decimal places. Also common sense tells us that a number around 5 multiplied by .24 will give us an answer less than 5, but more than zero.

Here's a problem which might fool some people: 


	   2.35
	 x  .24
	--------
	    940		<--- partial product one
	   470		<--- partial product two
	--------
	  .5640		<--- final product with decimal

	Since the answer ends with a zero we could change the
	answer to .564 and still have a correct answer since
	.564 = .5640. In this case, however, the answer would
	have only three decimal spots, but that's only because
	we got rid of an optional zero.

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