You are Here: Home >< Maths

# Core 1 Question differentiation; am I doing it right? Watch

1. Q) A cuboid has a volume of . The base of the cuboid is square with sides of length metres. The surface area of the cuboid is .

(i) Show that

I did and since there are two square sides multiplied this by two to get .

For the I just did since the volume is 8 then dividing by x would give surface area and I multiplied that by four because there are four rectangular surfaces.

So basically is that enough explanation for first one?

(ii) Find .

That is,

(iii) Find the value of which gives the smallest surface area of the cuboid justifying your answer.

Honestly I didn't know how to do this one; but check if what I did was right as a guess...

I thought since the volume is 8m^3 then surely the smallest value of each has to be 2? I'm not sure though - I stuck than in and got a minimum area of 12M^2.

So can someone check if I've done part 3 right especially and also if I haven't (the most likely case ) could you please explain how you do it?
2. Ah! You're doing the June 2006 past paper! That's quite a tricky one.
3. (Original post by Student#254)
Ah! You're doing the June 2006 past paper! That's quite a tricky one.
Yes haha!! There is no mark scheme online so I need help! Do you know the answer?
4. (Original post by Dededex)
Yes haha!! There is no mark scheme online so I need help! Do you know the answer?
Yes... Give me a sec.
5. (Original post by Student#254)
Yes... Give me a sec.
?
6. The last part is the part I'm most concerned about.

Hate the applications of differentiation questions.
7. (Original post by Dededex)
?
I get:

I was going to scan the solutions in, but my scanner isn't working!
8. (Original post by Student#254)
I get:

I was going to scan the solutions in, but my scanner isn't working!
Yeah that's kind of what I did however I didn't prove x = 2, I just assumed it since 2^3 is 8

Man I hate that question.
9. (Original post by Dededex)
Yeah that's kind of what I did however I didn't prove x = 2, I just assumed it since 2^3 is 8

Man I hate that question.
Yeah that paper has to be the hardest one I've tried so far...

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: December 4, 2010
Today on TSR

### Oxford interview invitations

When can you expect yours?

### Official Cambridge interview invite list

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.