Question

Teesha is in the French club. There are 31 students in the club. The French teacher will pick two students at random to guide visiting students from France. What is the probability that Teesha will be picked as a guide? Hint: Teesha must be picked first or second
A. 1/30
B. 30/31
C. 1/930
D. 2/31

Answer 1

just solved the same type of question....
http://openstudy.com/users/smokeysthename#/updates/51518fd7e4b0ae0b658be4da

Answer 2

Thank you hartnn, I'll take a look at that.

Answer 3

welcome ^_^
if you got any doubts, ask here, we'll clarify it here itself.

Answer 4

Thank you, will do. :b

Answer 5

Mhmm Mhmm so I went and looked............ I'm extremely lost o.o lol >.<

Answer 6

the probability that Teesha will be picked as a guide means
Teesha will be picked on 1st selection
AND
Teesha will be picked on 2nd selection

got this ?

Answer 7

Yesh

Answer 8

i would like to revise my previous statement,
the probability that Teesha will be picked as a guide means
Teesha will be picked on 1st selection and NOT in 2nd(because she's already selected),
AND
Teesha will be picked on 2nd selection and NOT in 1st.

Answer 9

Oooooh, so what happens then?

Answer 10

so, we'll consider 1st case,
Teesha will be picked on 1st selection and NOT in 2nd(because she's already selected),

1st selection, teacher has 31 choices, to select teesha, she has 1 option,
so, 1/31
2nd selection, teacher now have 30 other choices, and to NOT select teesha, she can pick any of 30 other, so 30/30
so, overall for 1st case, it'll be 1/31 *30/30
got this ?

Answer 11

I got it...... 30/930, does it need to be simplified?

Answer 12

1/31 + 30/31*1/30 = 2/31
how you got 30/930 ??

Answer 13

Lol............ ooooooh goodness, I multiplied 1/31 *30/30 o.o

Answer 14

ohh..for 1st case....30/30 =1 :P
i though you've got the final answer.

Answer 15

ok, did you understand 1st case ?
can i move to 2nd case ?

Answer 16

Yes please, moving on :b

Answer 17

2nd case,
Teesha will be picked on 2nd selection and NOT in 1st.,

1st selection, teacher has 31 choices, to NOT select teesha, she has 30 other options,
so, 30/31
2nd selection, teacher now have 30 other choices, and to select teesha, she have to pick her, so 1/30
so, overall for 1st case, it'll be 30/31*1/30 = 1/31
got this ?

Answer 18

since the 2 cases are independent, you'll add them,
1/31 + 1/31 = 2/31

Answer 19

Ok then

Answer 20

So 2/31 * 1/31 would = 2/31 as the answer? Lol, or am I too early?

Answer 21

1/31 + 1/31 = 2/31
thats why 2/31 is the answer as we considered both the cases.

Answer 22

Ohhhhhhh lol ok, I understand that now :b

Answer 23

Thank you [: You've been fanned lol.

Answer 24

thanks for fanning! :D
and welcome ^_^