A box contains 30 widgets, 4 of which are defective. If 4 are sold at random, find the probability that (a) all are defective (b) none are defective.

a. The probability that all are defective is 0.0003160493827

b. Probability that none are defective is 0.99968395

Step-by-step explanation:

Given that 4 of the 30 widgets contained on the box are defective, n = 4. The probability of picking a defective widget is p = 4/30 = 2/15.

Now, P(X = a) = (nCa)P^n(1 - P)^(n - a).

a. To find the probability that all are defective, we want to find P(X = 4)

= (4C4) × (2/15)^4 × (1 - 2/15)^(4 - 4)

= 1 × (2/15)^4 × 1

= 0.0003160493827

b. Probability that none are defective.

This is the same as saying (1 minus the probability that all are defective).

P = 1 - 0.0003160493827

= 0.99968395

answer: the answer is one of

step-by-step explanation:   we are given to write a proper fraction where the whole is divided into an even number of equal parts less than ten, and an odd number of those parts exist.

an even number less than 10 may be one of 2, 4, 6 or 8. so, the whole may be one of these four evens.

now, an odd number of these parts must exist, so the numerator must be an odd number, one of 1, 3, 5 or 7. it cannot be 9 because then the fraction will become improper.

thus, our fraction may be one of the following

a. she will receive a refund of $278.

step-by-step explanation: