Question

The probability that Sandra gets a ride to work on any morning is 0.7. The probability that she gets a ride 3 times in a 5-day work week is __, and the probability that she gets a ride at least 2 times in a 5-day workweek is __.

Answer 1

Answer: The probability that she gets a ride 3 times in a 5-day work week is 0.31.

The probability that she gets a ride at least 2 times in a 5-day workweek is 0.97.

Step-by-step explanation:

By binomial distribution formula:

$P[X=r]=^nC_rp^rq^{n-r}$ , where n is the number of trials , r is the number of success, p is the probability of success and q is the probability of failure.

Given : n=5

p = 0.7

q= 1-0.7=0.3

Now, the probability that she gets a ride 3 times in a 5-day work week :

$P[X=3]=^5C_3(0.7)^3(0.3)^{5-3}\\\\=10(0.7)^3(0.3)^2=0.3087\approx0.31$

The probability that she gets a ride at least 2 times in a 5-day workweek :

$P[X\geq2]=1-P[X$