Math – Applications for Living: The Point of It

In my Math – Applications for Living class, a couple of students did something humorous (and sad) with a problem on a quiz yesterday.

Here is the problem:

Computer sales for a certain company were reported to be $40.3 million in 2009.  This was stated to be a 12% increase over the prior year.  Find the computer sales for 2008 (round to the nearest tenth of a million).

We are working on translating a percent change to a multiplying factor (1.12 in this case), and most students are not there yet.  However, here is the thing these particular students did:

40,000,000.3   is ‘40.3 million’

I have not talked to these students about what led them to make this mistake; it looks like they think that ‘.3’ means that part is stuck after the decimal point.  Since we just started working with scientific notation, that type of error will be a large issue.

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