You are Here: Home >< Maths

# Indices- when to add or times?

Announcements Posted on
Last day to win £100 of Amazon vouchers - don't miss out! Take our quick survey to enter 24-10-2016

1. As you can see I got this question wrong and indices laws always confuse me. In the context of this question, how do you know when to add or multiply the indices together?

Posted from TSR Mobile
2. (Original post by jessyjellytot14)

As you can see I got this question wrong and indices laws always confuse me. In the context of this question, how do you know when to add or multiply the indices together?

Posted from TSR Mobile
You add indices when you multiply two things together. e.g.

You multiply indices when you are raising something to a power, e.g.
3. If the power is on the outside then you times the thing inside the bracket by itself the same number as the power, so for example (2x^3)^2 would become 4x^6 due to the 2 being squared and the 3 being multiplied by 2

or (2x^3)^3 would become 8x^9

However, in the case of something like 125 x 5^(0.5) it would become 5^3 x 5^(0/5), so that would become 5^(3+0.5) to become 5^(3.5)

I'm not great at explaining, but try these

12X^(4)Y^(2) x 2X^(2)Y^(3)

(12X^(4)Y^(2))^2

edit:
(Original post by 16Characters....)
You add indices when you multiply two things together. e.g. You multiply indices when you are raising something to a power, e.g.

nvrmind, the other guys is way simpler to understand
4. (Original post by jessyjellytot14)

As you can see I got this question wrong and indices laws always confuse me. In the context of this question, how do you know when to add or multiply the indices together?

Posted from TSR Mobile
Here's a quick intuitive feel for .

I'll do it with here to make life simpler, but it works for any :

and

So:

You now have a product of 's and 's and there are threes being multiplied in total.

Hence as expected.

-----------------------------------------------------------------------------------------------------

And here's a quick intuitive argument as to why is , it'll use the other theorem we 'proved' above.

You're comfortable that now, I hope.

So, since:

then we can simply add their powers:

Since (i.e: x added to itself y times) is just .

--------------------------------------------------------------------------------------

Basically, when you multiply two things, you add their powers. (if they are the same base). If you have a number to a power and raise it to another power then you multiply their powers.

But really, if you just sit down and read and understand the above, it should all make sense!
5. 16Characters.... C-rated Zacken Oh okay thanks, I understand it now in terms of bases
6. (Original post by jessyjellytot14)
16Characters.... C-rated Zacken Oh okay thanks, I understand it now in terms of bases
No problem!

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: May 16, 2016
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:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams