Math Help - Scientific notation

1. Originally Posted by yeKciM
correct answer is $\displaystyle \frac{(5.19\cdot 10^{-6})(8.3\cdot10^{5})}{2.07\cdot10^{4}} = 2.081 \cdot 10^{-4}$

to get it by calculator :

enter 5.16 then pres "exp" than 6 than "-" (+/- probably is written) than multiply "*" then enter 8.3 than "exp" than 5 pres "=" , than divede ( / ) than 2.07 again "exp" and 4.... press "=" again (you can do it without "=" before dividing but if you need to write down on paper .... ) than you will get 0.000208101 so now press "FIX" or something like that (depending on type of calculator , can be F -> E .... or something ) than you will get $2.081 \cdot 10^{-4}$
thats a different problem

you're partially correct as this needs to be rounded to sn 2.1x10^-4

2. Originally Posted by pychon
thats a different problem

you're partially correct as this needs to be rounded to sn 2.1x10^-4
depending for which is this needed is depending how accurate it should be ... because this is "small number" (0.0002081) it can be rounded to 2.1 on power of (-4) because this is close to it... when you round numbers you do it so that number after which you want to round (you say that is accurate for your need ... ) if number after that one like in this example is above 5 than that number is up by one ... if it was instead of 0.000208 it was 0.000202 than you will round it to 0.0002 so it means if is under 5 it stay there but if is more than 5 can be rounded to up by one... but that is depending on your needs ...

if you had capacitor 0.000000017 F you can't round that to 0.00000002 F because that will make big difference

3. Thanks for the help and corrections with this... one problem left on this sheet then two more pages of sn/en word problems and unit conversion :\ ; should have posted in univ maths.

Last problem is find the reciprocal of $9.02570\cdot10^{-18}$ . but im off to watch a few math videos to catch up.

4. Originally Posted by pychon
Thanks for the help and corrections with this... one problem left on this sheet then two more pages of sn/en word problems and unit conversion :\ ; should have posted in univ maths.

Last problem is find the reciprocal of $9.02570\cdot10^{-18}$ . but im off to watch a few math videos to catch up.
by hand or calculator ? just enter value and than you have mark written as "1/x" (probably is activated with that "2nd F" ) and you will get the reciprocal value
P.S there is no point in writing that last zero

5. Originally Posted by yeKciM
P.S there is no point in writing that last zero
Depending on the context there could be a point in writing the last zero.

Significance arithmetic - Wikipedia, the free encyclopedia

6. anyone around? need some major help with a few questions if someone wouldn't mind dedicating an hour... i've been swamped with things here. I have about 20 questions left in this assignment, taken notes, watched videos and still stumped. Questions are unit/metric conversion....

7. Originally Posted by pychon
anyone around? need some major help with a few questions if someone wouldn't mind dedicating an hour... i've been swamped with things here. I have about 20 questions left in this assignment, taken notes, watched videos and still stumped. Questions are unit/metric conversion....
Just post new threads, limit 1 question per thread or a small number of related questions per thread, I'm a bit predisposed but someone should be around to help out. Basically it's just common sense with posting but here are the rules

http://www.mathhelpforum.com/math-he...ng-151418.html

8. That's a bit too much... i will not sit here typing out new threads in the forum and flood it with each problem... some problems are trival, but my mind has been wracked with other things. It's 1am here and class in 6 hrs. So anyone who knows metric / unit conversion is welcomed to help. (I thought there was a "live" chat on this forum?)

9. Originally Posted by pychon
That's a bit too much... i will not sit here typing out new threads in the forum and flood it with each problem... some problems are trival, but my mind has been wracked with other things. It's 1am here and class in 6 hrs. So anyone who knows metric / unit conversion is welcomed to help. (I thought there was a "live" chat on this forum?)
Oh yeah the live chat doesn't work since a forum upgrade a little while back. Well I use the same approach with basically all unit conversions, I did one just a bit ago

http://www.mathhelpforum.com/math-he...tml#post555343

also this one

http://www.mathhelpforum.com/math-he...tml#post554018

Basically just write all units explicitly and make sure they cancel to give the desired end units. If it's simple enough you can be less explicit, but writing everything down carefully helps prevent mistakes, in my experience.

10. Originally Posted by undefined
Oh yeah the live chat doesn't work since a forum upgrade a little while back. Well I use the same approach with basically all unit conversions, I did one just a bit ago

http://www.mathhelpforum.com/math-he...tml#post555343

also this one

http://www.mathhelpforum.com/math-he...tml#post554018

Basically just write all units explicitly and make sure they cancel to give the desired end units. If it's simple enough you can be less explicit, but writing everything down carefully helps prevent mistakes, in my experience.

Though, none of it is making sense nor sticks... my brain is flooded. I've done the supplement work, taken notes, watched videos, read my univ pages and worksheets, it's simple math just stressed out. grrr

Example:
Code:
Write each metric measurement using the most appropriate prefix:
$8.19\cdot 10^5l$

I obtain 819kl

$67500 micro gram$

no idea... stuck

$2.041\cdot 10^-8MV$

no idea... stuck

$0.00002651 s$

=26.51 micro sec

$130.9\cdot 10^-10mA$

no idea... stuck

$9.5\cdot 10^6cm$

no idea... stuck

11. Originally Posted by pychon
Though, none of it is making sense nor sticks... my brain is flooded. I've done the supplement work, taken notes, watched videos, read my univ pages and worksheets, it's simple math just stressed out. grrr

Example:
Code:
Write each metric measurement using the most appropriate prefix:
$8.19\cdot 10^5l$

I obtain 819kl
819 kl is fine, but I think the question isn't very clear about the "most appropriate prefix". Should 0.05 metres be 5 cm or 50 mm? Of course it's subjective.

Originally Posted by pychon
$67500 micro gram$

no idea... stuck
67.5 * 10^3 * 10^-6 g = 67.5 mg

Originally Posted by pychon
$2.041\cdot 10^-8MV$

no idea... stuck
2.041 * 10^-8 * 10^6 V

You continue!

Originally Posted by pychon
$0.00002651 s$

=26.51 micro sec
Yes.

Originally Posted by pychon
$130.9\cdot 10^-10mA$

no idea... stuck
130.9 * 10^-10 * 10^-3 A

Continue.

Originally Posted by pychon
$9.5\cdot 10^6$

no idea... stuck
There are no units here.

There's probably a table like this in your book already, but if it helps,

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

12. last should have been $9.5\cdot 10^6 cm$

Have the prefix table memorized... i guess i'm falling short how to convert them properly.

Text from my supplement:
When the measurement is already in scientific notation, the power of ten in raised or lowered to offset the change that is made to the prefix.
Example:
convert
$7.2\cdot 10^4 kg to cg$
the prefix power change from 3 to -2 (down five)
so the power of ten is adjusted up 5 therefore $7.2\cdot 10^4 kg$ = $7.2\cdot 10^1 cg$
Having a hard time understanding that, especially when both prefixes are between centi to pico.

I don't see how you got:
67.5 * 10^3 * 10^-6 g = 67.5 mg

13. Originally Posted by pychon
last should have been $9.5\cdot 10^6 cm$

Have the prefix table memorized... i guess i'm falling short how to convert them properly.

Text from my supplement:

Having a hard time understanding that, especially when both prefixes are between centi to pico.

I don't see how you got:
67.5 * 10^3 * 10^-6 g = 67.5 mg
Your book says 7.2 * 10^9 cg right?

Anyway I recommend taking a step back here. What is 1 km? It is 1 * 10^3 m. The prefix simply multiplies your quantity by some predefined power of 10.

So for example 67500 micrograms, I rewrote as 67.5 * 10^3 micrograms, then 67.5 * 10^3 * 10^-6 grams, then 67.5 * 10^-3 grams, which is 67.5 mg

Remember a^b * a^c = a^(b+c)

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