You are Here: Home >< Maths

# Sort of easy maths question Watch

1. hey all, im bad at maths, can some one help me with this:

A person travels 121 miles from the town of Newville to the city of Ewee at an average speed of 75 mph and then returns home at a more leisurely 58 mph.
What was the average speed, correct to two decimal places, over the total distance covered?

The answer is = 65.41353.. = 65.41, correct to two decimal places.

Can some one pleeeeeease explain to me why that is the answer?

thanks!!
2. Avarage speed = total distance / total time.

So you need to calculate the time to get there and then time to get back to get total time. Total distance is just 121*2. Then plug these numbers into the formula.
3. (Original post by ttoby)
Avarage speed = total distance / total time.

So you need to calculate the time to get there and then time to get back to get total time. Total distance is just 121*2. Then plug these numbers into the formula.
So are you saying it is 121/75 + 121/58 ?
4. (Original post by T.I.)
So are you saying it is 121/75 + 121/58 ?
That will give you the total time. You can calculate that and plug that number into the formula:

Avarage speed = total distance / total time.
5. (Original post by ttoby)
That will give you the total time. You can calculate that and plug that number into the formula:

Avarage speed = total distance / total time.

So it is (121/75) + (121/58) = (1.613333333 + 2.086206897) = 3.69954023

121*2 = 242

242/ 3.69954023 = 65.41353383 = 65.41

Is that right buddy?
7. (Original post by tehforum)
I was just checking the workings, as i did that the first time around and got it wrong. grrrrrr.

Do you know much about standard deviation?

I have been asked the question:

Find out the estimated standard deviation, using the n – 1 divisor, of the data.

What would i have to do?

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 10, 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.