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# What is the answer to 68 billion minus 12 million?

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2009-10-20 20:42:45

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Sixty-Eight Billion Minus Twelve Million Equals?

68,000,000,000 - 12,000,000 = 67,988,000,000

When you do the arithmetic on paper, arrange the numbers vertically, but make sure that you align the numbers from the right, so that the units place digits align, the tens place digits align, and so on.

You can save yourself the trouble or writing a lot of zeros -- and perhaps misaligning the digits -- if you think of one billion as a thousand million; that is, 1 billion = 1,000 million. So, 68,000,000,000 (68 billion) is the same as 68,000 million. That makes the subtraction a bit easier, because now you can just subtract 12 (million) from 68,000 (million). 68,000 minus 12 equals 67,988. But remember that's 67,988 million, which is written 67,988,000,000.

Rounding errors

In practice, if someone has given you a number ending in a lot of zeroes, then it has almost certainly been rounded. For instance, the population of the UK is around 58 million. It might be 58,437,097 , it might be 57,218,643 - no one knows or cares exactly what it is. Of those people, 659 are Members of Parliament.

Suppose someone asks "How many people in the UK are NOT MPs?". It would be silly to give the answer 58,000,000 - 659 = 57,999,341 , when we only know the answer to the nearest million. So the 659 are negligible, and the number of non-MPs is 58 million (or near enough).

In the same way, it is true that 68 billion minus 12 million is 67,988,000,000 . But whatever you need the answer for, a more sensible one would probably be that you can just ignore the 12 million and call the answer 68 billion.

2009-10-20 20:42:45