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Sort of easy maths question

T.I.

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!!

Reply 1

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.

Reply 2

T.I.

Original post by ttoby

So are you saying it is 121/75 + 121/58 ?

Reply 3

ttoby

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.

Reply 4

T.I.

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?

Reply 5

tehforum

Evidently, as you posted the answer in your OP.

Reply 6

T.I.

Original post by tehforum

Evidently, as you posted the answer in your OP.

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?