Teaser-2

[empip]

Pip was driving at a steady rate he noticed the road edge marker posts appeared to be regularly spaced. He mused on their spacing ... So he set his stopwatch then counted the posts passed in one minute. Hmmm, the number of posts passed was exactly one fifteenth of his speed in MPH.
Assuming a steady driving pace, equally spaced posts, timing beginning and ending midway twixt two posts

What was the distance between those posts in feet?

 

[johnny_t]

Lets call.....

Speed in mph V
Distance between posts L
Number of posts passed n


Distance travelled in 1 minute = (v x 5180 (ft/mile))/60 = 86.333V
Is also equal to (n-1)L + L/2 + L/2 = nL

So 86.33V = nL

Substitute v/15 for n, 86.33V = (V/15)L = VL/15

Move the 15,

(86.33 X 15) V = V L

so L = 86.33 x 15 or 1295 ft



Do I get extra points for showing my working ??

 

[empip]

Lets call.....
Speed in mph V
Distance between posts L
Number of posts passed n
Distance travelled in 1 minute = (v x 5180 (ft/mile))/60 = 86.333V
Is also equal to (n-1)L + L/2 + L/2 = nL
So 86.33V = nL
Substitute v/15 for n, 86.33V = (V/15)L = VL/15
Move the 15,
(86.33 X 15) V = V L
so L = 86.33 x 15 or 1295 ft

Do I get extra points for showing my working ??

Nah !! Nearly ... just 100 ft out in your version of a mile. but only 25 ft in the answer ..
====================
Let P be the number of posts passed in one minute.
In an hour, the car will pass 60P posts. The speed of the car is 15P miles per hour. In 15P miles, it will pass 60P ÷ 15P = 4 posts.
The post spacing is 0.25 miles 1320 ft

Simply number of posts in one hour divided by distance in one hour.

Bish bash bosh !

 

[johnny_t]

This proves the value of showing the working.....

Apparently there are now 5280 feet in a mile (probably the human rights act again), so if I plug that into the above, 1320 ft does pop out the bottom.

EDIT: Bah - You edited yours whilst I was writing mine

 

[empip]

At least I checked your working ...

5,280 Ft only since the time when there have been 1,760 yds.

 

[Steve]

Pip was driving at a steady rate he noticed the road edge marker posts appeared to be regularly spaced. He mused on their spacing ... So he set his stopwatch then counted the posts passed in one minute. Hmmm, the number of posts passed was exactly one fifteenth of his speed in MPH.
Assuming a steady driving pace, equally spaced posts, timing beginning and ending midway twixt two posts

What was the distance between those posts in feet?

never mind the posts, watch where you're going.