Math Help - a maths problem

1. a maths problem

hello i wanted to ask a maths problem i'm in year 11 in victoria, australia. i'm doing general maths advanced which is the hardest maths in my year level.....ok here it is...a cyclist goes up a long slope at a constant speed of 15 km/h he turns around and comes down the slope at constant spped of 40 km/h find his average speed over a full circuit...this is the problem..i have doing maths from last 24 hours and i'm really tired i tried it at 1 pm last night but couldn't because i wanted to sleep anyway...i hope someone helps me....(the answer is 240/1 km/h i only want to know how did they get it ) thnx in advance

2. Originally Posted by ziggy777
hello i wanted to ask a maths problem i'm in year 11 in victoria, australia. i'm doing general maths advanced which is the hardest maths in my year level.....ok here it is...a cyclist goes up a long slope at a constant speed of 15 km/h he turns around and comes down the slope at constant spped of 40 km/h find his average speed over a full circuit...this is the problem..i have doing maths from last 24 hours and i'm really tired i tried it at 1 pm last night but couldn't because i wanted to sleep anyway...i hope someone helps me....(the answer is 240/1 km/h i only want to know how did they get it ) thnx in advance
Here is an outline - the details are left for you:

Up the slope: $t_1 = \frac{L}{15}$

Down the slope: $t_2 = \frac{L}{40}$

Average speed $= \frac{2L}{t_1 + t_2}$.

3. wait a minute this is a new formula where did you get that? what is L would you please explain..

thank you for your quick help...

4. L would be the distance travelled up or down the slope.

5. Originally Posted by Prove It
L would be the distance travelled up or down the slope.
I was hoping that someone "doing general maths advanced which is the hardest maths in my year level" would figure that out.

Distance = (speed) (time) ....

6. Originally Posted by mr fantastic
I was hoping that someone "doing general maths advanced which is the hardest maths in my year level" would figure that out.

Distance = (speed) (time) ....
Everyone draws a blank every now and then Mr F...