Question

Ms. Smith has 30 students in her class: 20 are boys and 10 are girls. Mr. Jones also has 30 students in his class: 15 are boys and 15 are girls. One student is selected from each class to be on the student council. What is the probability that 2 boys are selected?

A. 1/6

B. 1/3

C. 1/2

D. 7/12

Answer 1

what do you think the total possible combination is?

Answer 2

I am not sure but I was thinking A or C

Answer 3

well, let's look at this way.

How many students are there in Ms. Smith class room?

Answer 4

Ms Smith has 30 students

Answer 5

good. How about Mr. Jones class?

Answer 6

30

Answer 7

good. So if select one student form each class, and pair them up. How many pairs can you form?

Answer 8

2

Answer 9

no no, how many PAIRS can be formed?

Answer 10

Oh, 15 pairs

Answer 11

no. it's 30 * 30 = 900 pairs possible. Why?

Answer 12

Because they have 30 students from one class and 30 students from the other class?

Answer 13

Good.

Now how many boys are there in Ms. Smith class?

Answer 14

20 boys

Answer 15

good. What about the other one?

Answer 16

15 boys

Answer 17

so if you select each boy from each class, how many pairs of boys can be formed?

Answer 18

There are 15 pairs?

Answer 19

no, it's 20 * 15 = 300

Answer 20

so the probability that a pair contains two boys is?

Answer 21

Do you always multiple in probability?

Answer 22

no, you don't always multiply.

Answer 23

1 pair

Answer 24

???

Answer 25

P = 300/900 yes?

Answer 26

So, 300 times 2=900 because the 300 part is from the two class and the 2 is from the two boys.

Answer 27

two classes*

Answer 28

300 * 2 isn't 900.

answer is 300/900 = 1/3 so B

Answer 29

I feel like you still haven't fully understood why we did what we did.

Answer 30

Yeah, a little bit. I hardly learned about probability.

Answer 31

But, I truly thank you for using your time helping me step by step.

Answer 32

what grade are you in?

Answer 33

9th

Answer 34

huhm... that's probably why. Probability isn't easy for middle high schoolers. Not because it's hard but because probabilities requires thinking logically, which is too advanced for a 9th grader.

Answer 35

Pretty suck for me. But, I am willing to learn! :) Thank you

Answer 36

it takes times and practices. As long as you're willing to learn, you'll get better :)