Aptitude - Probability - Discussion
Discussion Forum : Probability - General Questions (Q.No. 7)
7.
In a class, there are 15 boys and 10 girls. Three students are selected at random. The probability that 1 girl and 2 boys are selected, is:
Answer: Option
Explanation:
Let S be the sample space and E be the event of selecting 1 girl and 2 boys.
| Then, n(S) | = Number ways of selecting 3 students out of 25 | |||
| = 25C3 ` | ||||
|
||||
| = 2300. |
| n(E) | = (10C1 x 15C2) | ||||||
|
|||||||
| = 1050. |
 P(E) = |
n(E) | = | 1050 | = | 21 | . |
| n(S) | 2300 | 46 |
Discussion:
54 comments Page 6 of 6.
Ronald said:
2 years ago
I don't understand the answer, please someone help me.
(7)
DINESH D S said:
2 years ago
@All.
Here is the simple explanation.
There are 3 possiblities (gbb, bbg, bgb)
Let's take 1st one GBB
Getting girl as prob is 10/25.
Getting boy as prob is 15/24 (as 1 is already taken as girl..sample space is 24).
Getting 2nd boy is 14/23(as 1 boy is already chosen (numerator and denominator(samplw space) are reduced by 1))
Since 3 possibilities 3*(10/25*15/24*14/23).
Will give you the answer 21/46.
Here is the simple explanation.
There are 3 possiblities (gbb, bbg, bgb)
Let's take 1st one GBB
Getting girl as prob is 10/25.
Getting boy as prob is 15/24 (as 1 is already taken as girl..sample space is 24).
Getting 2nd boy is 14/23(as 1 boy is already chosen (numerator and denominator(samplw space) are reduced by 1))
Since 3 possibilities 3*(10/25*15/24*14/23).
Will give you the answer 21/46.
(37)
Varshini said:
11 months ago
Total (boys and girls)==>25.
Girls can be selected in 10 ways ==>10/25.
Boys can be selected in 15 ways ==>15/24 * 14/23.
Here boys are repeated twice so we can write the total equation like this;
==> (10/25)*(15/24)*(14/23)*(3!/2!).
So by solving the above equation, we get ==> 21/46.
Note: Why I am taking 3!/2! means total 3 students are selected so ==>3! and boys repeated twice so divide by ==> 2!.
Girls can be selected in 10 ways ==>10/25.
Boys can be selected in 15 ways ==>15/24 * 14/23.
Here boys are repeated twice so we can write the total equation like this;
==> (10/25)*(15/24)*(14/23)*(3!/2!).
So by solving the above equation, we get ==> 21/46.
Note: Why I am taking 3!/2! means total 3 students are selected so ==>3! and boys repeated twice so divide by ==> 2!.
(7)
Daniel ocen said:
3 months ago
I can't understand this, someone help me to get it.
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