You are Here: Home >< Maths

# Help w MathsðŸ™ƒ Watch

Announcements
1. T to the power 3= mn/m-n

M=4x10 to the power 12
N=3x10 to the power 9

Work out T.

Eh I multiplied m and n together (to get MN) and got 12x10 to the power 21 (I know you can't have numbers above 12 in standard form but I have no idea whether what I'm doing is correct).

Then I did m-n and got 1x10 to the power 3.

Did the division sum= 12x10 to the power 21 divided by 1x10 to the power 3 and got 12x10 to the power 18=1.2x10 to the power 19.

T to the power 3= 1.2x10 to the power 19.

'Cube rooted' it and the answer I got for T was 2289428.485.

It wants the answer in standard form to 3 significant figures= 2.29x10 the power 6.

Is this completely wrong or? Probably just over complicated a really simple question but help would be appreciated
2. (Original post by idfk_)
X
Your first step (m x n) is correct. However, is not . Adding and subtracting gets a bit more complicated if the tens are to different powers (you do not subtract the exponents if you're just doing subtraction) so if you're not using a calculator, you need to manually put them to the same power. so .
3. (Original post by Plagioclase)
Your first step (m x n) is correct. However, is not . Adding and subtracting gets a bit more complicated if the tens are to different powers (you do not subtract the exponents if you're just doing subtraction) so if you're not using a calculator, you need to manually put them to the same power. so .
Thankyou!!

So, would I go about it the same way when I do the division and then cube root the answer to get to T?
4. (Original post by idfk_)
Thankyou!!

So, would I go about it the same way when I do the division and then cube root the answer to get to T?
So you now know what and are ( and respectively) so yes, you just do a simple division. You will probably want to do this on your calculator though, unless you're particularly keen on working out what is by hand!
5. (Original post by Plagioclase)
So you now know what and are ( and respectively) so yes, you just do a simple division. You will probably want to do this on your calculator though, unless you're particularly keen on working out what is by hand!
Calculator it is.

From that I get the answer 3002251689. Cube root it to get T=1442.610313

Which is equal to 1.44x10 to the power 3?
6. (Original post by idfk_)
Calculator it is.

From that I get the answer 3002251689. Cube root it to get T=1442.610313

Which is equal to 1.44x10 to the power 3?
Yep, that's what I've got!
7. (Original post by Plagioclase)
Yep, that's what I've got!
Again, thanks a lot! Wouldn't have got to that myself

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: September 26, 2016
Today on TSR

### How would you do in an Oxford interview?

Put yourself through the test

### STI without any sexual activity?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.