AP BIOLOGY

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HEREDITY

BASICS OF PROBABILITY

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
A box contains 3 black pens, 7 blue pens, and 5 red pens. Without looking, Juan randomly picks a red pen out of the box. If he chooses another pen out of the box without replacing the first one, what is the probability that he will pick a red pen both times?
A
2/21
B
1/9
C
5/42
D
9/29
Explanation: 

Detailed explanation-1: -– 2880 = 40320 – 2880 = 37440. 9. In how many ways 2 red pens, 3 blue pens and 4 black pens can be arranged if same color pens are indistinguishable? Explanation: Total number of pens are 2+3+4 = 9 out of which 2 are of 1 type, 3 are of 2nd type and 4 are of 3rd type.

Detailed explanation-2: -Since every pen is either black or red the probability of drawing either a black or red pen is 100%.

Detailed explanation-3: -Total probability of getting first blue and second black pen = 12/30 × 18/29 = 36/145. ∴ The probability of getting the first blue and second black pen is 36/145. UPSC EPFO APFC New Notification is expected to be released in September 2022.

Detailed explanation-4: -The ratio of blue pens to red pens is 5:7.

There is 1 question to complete.
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