Today I asked my dad how many seconds are in a century.

So he took out a piece of paper and we figured it out.

And here is our equation:

60sec/1minute · 60min/1hour · 24hours/1day · 365days/1year · 100years/1century = seconds in a century

This is called the factor-label method. All those fractions after the first one are actually equal to one.

When we multiply it out, most of the labels cancel out:

60sec/1

Now we have to do the arithmetic:

60 · 60 · 24 · 365 · 100 = seconds in a century

We tried doing it on a calculator, but the answer was too big!

So we factored it:

36 · 24 · 365 · 10

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And multiplied the first part on the calculator:

315,360 · 10

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^{Then we added four zeroes:}

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3,153,600,000

There are over 3 billion seconds of in a one hundred year period!