John runs a computer software store. Yesterday he counted 125 people who walked by the store, 66 of whom came into the store. Of the 66, only 21 bought something in the store. (Round your answers to two decimal places.) (a) Estimate the probability that a person who walks by the store will enter the store.

(b) Estimate the probability that a person who walks into the store will buy something.

(d) Estimate the probability that a person who comes into the store will buy nothing.

A. Divide number of people in the shop by total people walking by:

66/125 = 0.528 = 0.53

B. Divide people who bought something by total people walking by:

21/125 = 0.168 = 0.17

d. 66 -21 = 45 people don’t buy anything.

45/66 = 0.68

The number of students in the class is 21

Step-by-step explanation:

The first thing to consider is Andy.

Let x be the number of students who are taller than Andy.

Then the number of the rest students, excluding Andy, is 4x, according to the condition.

So, the total number of students in the class is (x + 4x + 1), or 5x+1.

Next, consider Violetta.

Let y be the number of students who are shorter than Violetta.

Then the number of the rest students, excluding her, is 3y, according to the condition.

So, the total number of students in the class is (y + 3y + 1), or 4y+1.

We see, that the number of students in the class MINUS one is a multiple of 4 (four) and of 5 (five), at the same time.

So, the number of students in the class is EITHER 20+1 = 21 OR 40+1 = 41, if consider couple of minimal values.

But 41 is excluded by the condition, leaving a UNIQUE ANSWER:

The number of students in the class is 21.