Story Problem:Measured rate of crystal growth is 1mm in 16 months.The Crystals are believed to be 400,000 yrs. old. How long in meters?

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Detail explanation of Acetek: We assume the growth rate is a linear.

First we must convert the time in the same unit. Lets find out how many month are there in 400,000 year. There are 12 month in a year so:

400,000 * 12 = 4,800,000 months

Next we calculate the size of the crystal. We know that in 16 months the crystal grows 1 mm, so lets find out how many 16 months goes into 4,800,000 months.

4,800,000 / 16 = 300,000 mm

Now all that left is to convert mm to m. 1000mm equals to 1 m

300,000 / 1000 = 300m

PM me if the answer is different

So you need to find out how much it grows in a single year (12 months). Set it up as a proportion:

1mm/16months = (x)mm/12months

Cross multiple and solve for x. Whatever the value of x is, multiply it by 400,000. When you get this number, divide it by 1,000, in order to convert mm to meters. That is your answer