Answer:
They studied for a little more than an hour?
Step-by-step explanation:
7/12 of 60 Mins is 35 mins and 2/3 is 40 mins 40+35=75 mins
which is a little more than an hour, 15 mins more to be precise.
Answer:

And we can assume a normal distribution and then we can solve the problem with the z score formula given by:

And replacing we got:


We can find the probability of interest using the normal standard table and with the following difference:

Step-by-step explanation:
Let X the random variable who represent the expense and we assume the following parameters:

And for this case we want to find the percent of his expense between 38.6 and 57.8 so we want this probability:

And we can assume a normal distribution and then we can solve the problem with the z score formula given by:

And replacing we got:


We can find the probability of interest using the normal standard table and with the following difference:

y= -x/2 + 1 is the answer
Answer:
80
Step-by-step explanation:
I used a calculator to solve