There are 75 students in a speech contest. Yesterday 1/5 of them gave their speech. Today, 3/5 of the remaining students gave their speeches. How many students still haven't given their speeches?

39 students.

Step-by-step explanation: 1/5 of 75 is 60. Now we need to find out what 3/5 of 60 is. 3/5 times 60 = 39. 39 students need to give their speeches.

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! )