Answer:
probability that he or she will answer at least 4 problems correctly = 0.5
Step-by-step explanation:
probability that he or she will answer at least 4 problems correctly is given as;
P (at least 4 correctly) = P (exactly 4 correctly) + P (all 5 correctly)
Since there are 10 problems. 4 is from the 7 problems chosen and 1 is from the 3 problems we can't figure out. Thus, P(exactly 4 correctly) = 7C4 x 3C1
Thus, P (at least 4 correctly) = [ (7C4) x (3C1) ] / (10C5)] + [(7C5)/(10C5)]
= [(35 x3)/252 ] + [21/252]
= [ 105/252 ] + [ 21/252 ]
= 126 / 252
= 0.5
so two fellows did all the carpeting in 10 days.
now, how long did "1" fellow work only? well, it worked for 10 days.
how long did the other fellow work for? well, it was working alongside the first one, and it was there for also 10 days.
so the two guys working together, really did 10+10 = 20 "days worth of work". So that the whole carpeting job can be done in 20 "days worth of work".
now if we want to finish it in 4 days, 20 ÷ 4 = 5.
so if we hire 5 guys, since each one will do 4 days worth, 5*4 = 20 <- the whole job.
1 hour and 30 minutes because when you subtract those you will get that answer
Answer:
80%
Step-by-step explanation:
To find percent decrease (new amount/original amount)*100
(500/625)*100
=80
--
to check
625*.80
=500
or
625*80%
=500
