B How can I perform decimal computation by hand?

[Mr Davis 97]

I have to perform the following computation by hand to get a number within two decimal places:
$\displaystyle (120)(\frac{54.30}{194.79})$. The answer is 33.45, but how can I do this by hand?

 

[SteamKing]

I have to perform the following computation by hand to get a number within two decimal places:
$\displaystyle (120)(\frac{54.30}{194.79})$. The answer is 33.45, but how can I do this by hand?

Well, the multiplication part should be easy enough. It's the long division which takes a bit more effort.

Remember, $$a ⋅ \frac{b}{c} = \frac{a ⋅ b}{c}$$

Don't tell me you've never done any arithmetic by hand.

 

[jedishrfu]

multiply top and bottom by 1 ie 100/100 to get 120 * 5430/19479

next use long division

You could first multiply the numerator by 120 before you divide

 

[Mr Davis 97]

Okay, so doing the long division $\frac{651600}{19479}$ I can get to 33, but then I have the remainder $\frac{8793}{19479}$. How can I figure out that this remainder is approximately 0.45?

 

[jedishrfu]

Have you forgotten how to do long division?

Here's an example image:

 

[jedishrfu]

Here's some video tutorials to help you:





and there are more here:

https://dl.dropboxusercontent.com/u/28928849/Webpages/ArithmeticVideoLibraryTable.htm

from mathispower4u.com