Simplying a problem with decimals and exponents

[Anna Blanksch]

1. Homework Statement

(2.5 x 10^24)(4.5 x 10^-9) / (3 x 10^4)

Homework Equations

The Attempt at a Solution

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I know that when multiplying base ten numbers with exponents you add the exponents (ie: 10^2 x 10^3 = 10^5) ad that when dividing, the exponents are subtracted. I'm not sure what my first step would be towards simplifying this equation.

 

[Dick]

1. Homework Statement

(2.5 x 10^24)(4.5 x 10^-9) / (3 x 10^4)

Homework Equations

The Attempt at a Solution

[/B]
I know that when multiplying base ten numbers with exponents you add the exponents (ie: 10^2 x 10^3 = 10^5) ad that when dividing, the exponents are subtracted. I'm not sure what my first step would be towards simplifying this equation.

Split it into ((2.5 x 4.5)/3) x ((10^24 x 10^(-9))/10^4). Use your exponent rules on the second factor and a calculator on the first factor.

 

[Anna Blanksch]

Great! Thanks for your help. Is there a rule/title for the process of converting from the original problem to the way that you split it (separating the base ten numbers)? Also, am I calling those the right thing? Base ten numbers? Should they be called, "base ten exponents"? The answer I got is 3.75 x 10^11. Close? Right on? Thanks again so much for your quick reply!

 

[Dick]

Great! Thanks for your help. Is there a rule/title for the process of converting from the original problem to the way that you split it (separating the base ten numbers)? Also, am I calling those the right thing? Base ten numbers? Should they be called, "base ten exponents"? The answer I got is 3.75 x 10^11. Close? Right on? Thanks again so much for your quick reply!

Right on. I call them "powers of ten", and I don't think it has a name. It's just separating the powers of ten from the other numbers.

 

[SteamKing]

Is there a rule/title for the process of converting from the original problem to the way that you split it (separating the base ten numbers)?

What you are seeing is an application of the associative property in multiplication:

http://en.wikipedia.org/wiki/Associative_property

You can use this property to group strings of numbers being multiplied together into more convenient arrangements.

For example:

(2 * 3) * 4 = 2 * (3 * 4) or
(2 * 10³) * (4 * 10²) = (2 * 4) * (10³ * 10²) = 8 * 10⁵

 

[BvU]

Poor Anna, in the middle of nitpicking nerds !

I can't resist to point at the sentence "Associativity is not to be confused with commutativity, which addresses whether a × b = b × a." in his majesty's link. However, you need it to get from where you were to where you want to be.

If you go on in maths or physics this kind of attention to detail is essential; for the rest of the world it's just a good idea :)

 

[SteamKing]

It's learning the simple things which seems to be overlooked nowadays. Everybody wants to split the atom; nobody wants to learn to use a hammer.