Question

2 bananas are to be selected from a group of 5. In how many ways can this be done?

Answer 1

When you pick the first banana, there are 5 to choose from, when you pick the second, there will be four. (5)(4) = 20. But, if i pick banana 1 then banana 3, or if i had picked banana 3 then 1, thats the same outcome, so I need to divide by 2.

Answer is 10 i believe.

Answer 2

thats not an answer option....

Answer 3

hmmm...what are the answer choices?

Answer 4

1, 20, 120, and not "here" i get worried iwth the not here's :s

Answer 5

lol, yeah, those "not here" answers freak me out too.

Another way to compute the answer is to do \[\left(\begin{matrix}5 \\ 2\end{matrix}\right)\]
which is read "5 choose 2", or, "the number of ways to choose 2 objects at a time from 5 objects" have you seen this before?

Answer 6

yes, and i guess the more i think about it, 10 seems right......oiy!

Answer 7

yeah, the answer is still 10 after computing that, I'll put my money on "Not Here" :)

Answer 8

10

Answer 9

okay :)

Answer 10

here we go

Answer 11

hey i have another one, ill do it and could u check it?

Answer 12

yes

Answer 13

sure

Answer 14

2 bananas are to be selected from a group of 6. In how many ways can this be done?
i think the answer is 30?

Answer 15

15

Answer 16

but in that last one we multiplied

Answer 17

When i pick the first banana, there are 6 to choose from, then 5 for the second.
(6)(5) = 30
But (just like the last problem) i have to divide by 2
Answer should be 15

Answer 18

ohhhhhhh now i seee!

Answer 19

You own 10 hats and are taking 2 on vacation. In how many ways can you choose 2 hats from the 10?
so for this one the answer would be......45?

Answer 20

yes :)

Answer 21

general formula

for choosing r things out of n things

no of ways = n!/ r!(n-r)!

Answer 22

SWEET! i think im actually understanding this stuff! ooh quick while im on a role lets do another one!

Answer 23

9 students volunteer for a committee. How many different 7-person committees can be chosen?
181,440????

Answer 24

That is a good formula to know :)
\[\left(\begin{matrix}n \\ r\end{matrix}\right) = \frac{n!}{r!(n-r)!}\]

Answer 25

or would it be 362,880

Answer 26

So you want to compute \[\left(\begin{matrix}9 \\ 7\end{matrix}\right) = \frac{9!}{7!(9-7)!}\]
= 36

Answer 27

oh....hmmmmlets try a diff one i will get 1 i have to !!!!

Answer 28

oops wrong 1

Answer 29

sure thing, i would really try to get the formula down, for smaller numbers (like the banana and hat problem) you can rationalize an answer. But for larger numbers the formula works best

Answer 30

6 students volunteer for a committee. How many different 3-person committees can be chosen?

Answer 31

20

Answer 32

what do u do after u have 6?3(6-3)?????

Answer 33

So you have 6 people, and you want to choose 3, so:
\[\left(\begin{matrix}6 \\ 3\end{matrix}\right) = \frac{6!}{3!(6-3)!}\]

Answer 34

\[=\frac{(6)(5)(4)(3)(2)(1)}{(3)(2)(1)(3)(2)(1)}\]

Answer 35

what is that ? and what do i do with it ? do i divide or do i multiply???

Answer 36

Simplifying by cancelling out the things that are the same in the numerator and denominator we get:
\[\frac {(6)(5)(4)}{(3)(2)(1)} = \frac{120}{6} = 20\]

Answer 37

oh i see now! ok let me save the formula .... 1 sec. DONT GO ANYWHERE! lol (please)

Answer 38

You and two friends visit a pizza shop. There are 12 toppings. 7 toppings are meat and the rest are vegetable. Each of you orders a different topping (no repeats) at random. What is the probability that your group orders only meat toppings?
i think the answer is 7/44 (im prob. wrong)

Answer 39

Wow, alright let me think about this lol...you are going to pick 2 toppings. there are 12 total toppings, so:
\[\left(\begin{matrix}12 \\ 2\end{matrix}\right) = 66\]
is the total number of combinations (including vegies and all that).
Now lets see how many of those combinations only have meat.
That would be \[\left(\begin{matrix}7 \\ 2\end{matrix}\right) = 21\]
So the probability is:
\[\frac{21}{66} = \frac{7}{22}\]

Answer 40

gtg

Answer 41

ACK!! there are 3 people, my stuff is wrong, i just noticed, you are probably right

Answer 42

alright, sry bout the mix up.

Answer 43

Your answer is correct, just calculated it

Answer 44

how does this make sense? O.o

Answer 45

honestly i have NO CLUE! lol

Answer 46

this is freshman stuff? i didnt go through this....