The time between phone calls at Jawwal center has an exponential distribution with average of 40 40
seconds. What is the probability that the time is at least 55
55
seconds?
Select one:

a.
0.2528
0.2528

b.
0.4832
0.4832

c.
0.4169
0.4169

d.
0.7472
0.7472

e.
0.3189

where are the choices?

-7/8

step-by-step explanation:

instead of subtracting you add the -6/8 and -1/8

hello from mrbilldoesmath!

answer:   x (x+6)^2, choice b

discussion:

factor x out of the equation:

x^3 + 12x^2 + 36x = x (x^2 + 12x + 36).

note that 6+6 = 12 and 6*6 = 36 so the above factors into:

x (x+6)^2

which is choice b

you,

mrb