You are Here: Home >< Maths

# C3 Differentiation help please :) Watch

1. Some students on an expedition reach the corner of a very muddy field. They need to reach the opposite corner as quickly as possible. They estimate they can walk along the edge of the field at the rate of 5km/h, and then cut across the field at 3km/h. The field is a square of 0.5km.

How far do they need to walk along the field before cutting across?
--

How would you go about solving this? I'm struggling a little bit with the wording of it. I know I will have to use the chain rule and I have got a few ideas but it would really help me if someone could explain it to me.

Thank you
2. (Original post by tommydeaks)
Some students on an expedition reach the corner of a very muddy field. They need to reach the opposite corner as quickly as possible. They estimate they can walk along the edge of the field at the rate of 5km/h, and then cut across the field at 3km/h. The field is a square of 0.5km.

How far do they need to walk along the field before cutting across?
--

How would you go about solving this? I'm struggling a little bit with the wording of it. I know I will have to use the chain rule and I have got a few ideas but it would really help me if someone could explain it to me.

Thank you
They need to walk x km along the field
Then the the way across the field will

Write down the time as the function of x, and determine the minimum.

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 7, 2010
Today on TSR

### Cambridge interview invitations

Has yours come through yet?

### Official Oxford 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.