Rebecca ran 21 miles in 5 hours. If she ran at a constant speed, how many miles did she run in 2 hours? 8.4 miles 42 miles 4.2 miles 1.2 miles

8.4 miles

Step-by-step explanation:

d = rt

Solve for her rate

21 = 5r

r = 21/5

r = 4.2

Solve for if the time is 2 hours and rate (solved previously) is 4.2

d = 4.2*2

d = 8.4

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )

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step-by-step explanation:

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