Question

Let an integer be chosen at random from the integers 1 to 30 inclusive. Find the probability that the integer chosen is divisible by 3.
9/30
11/30
1/3

Answer 1

@iGreen

Answer 2

Um, what numbers are divisible by 3 between (and including) 1 and 30?

Just find the first 10 multiples of 3.

Answer 3

3 * 1 = ?
3 * 2 = ?
3 * 3 = ?
3 * 4 = ?
3 * 5 = ?
3 * 6 = ?
3 * 7 = ?
3 * 8 = ?
3 * 9 = ?
3 * 10 = ?

Answer 4

Well, we don't even have to find them..just count how many there are.

Answer 5

Sorry net is moving slow, or maybe it's the site. :/

3,6,9,12,15,18,21,24,27,30,33,36

Answer 6

@iGreen

Answer 7

Okay, count the one's between 1 and 30, how many are there?

Yeah, it's Open Study's site.

Answer 8

11, correct?

Answer 9

@iGreen

Answer 10

No..check again.

Answer 11

9? I thought I was supposed to include 1 and 30.

Answer 12

No, 9 is wrong too..1 is not a multiple of 3.

Answer 13

1 is not divisible by 3*

Answer 14

3 * 1 = 3
3 * 2 = 6
3 * 3 = 9
3 * 4 = 12
3 * 5 = 15
3 * 6 = 18
3 * 7 = 21
3 * 8 = 24
3 * 9 = 27
3 * 10 = 30

@igreen

Answer 15

Yep, and how many is that?

Answer 16

You gave me 10 problems. Or are you talking about the 30?

Answer 17

Yes, 10 problems..

Answer 18

Since there are 10 numbers that are divisible by 3 between (and including) 1 and 30, the probability of picking a number divisible by 3 is 10/30.

You can simplify 10/30, and what is that?

Answer 19

1/3

Answer 20

Yep, so that's your answer.

Answer 21

Thanks Green!