Question

The probability of guessing the correct answer to a certain test questions is x/12. If the probability of not guessing the correct answer to this question is 2/3, then x =
(a)2
(b)3
(c)4
(d)6

Answer 1

SOLUTION :  

The correct option is (c) : 4

Given : The probability of guessing the correct answer to certain question = x/12

The probability of not guessing the correct answer for the same question = ⅔

The sum of all the probabilities of all possible outcomes of experiment is 1.

P(Event) + P (not an Event) = 1.

P(guessing the correct answer) + P(Not guessing the correct answer) = 1  

x/12 + ⅔ = 1

x/12 = 1 - ⅔  

x/12 = (3 - 2)/3

x/12 = ⅓  

3x = 12

x = 12/3  

x = 4

Hence, the value of x is 4 .

HOPE THIS ANSWER WILL HELP YOU ...

Answer 2

Hey mate!

We know that,
P(E)+P(not E) = 1
So,
(x/12)+(2/3) = 1
(x+8)/12 = 1
x+8 = 12
x = 4
So, the answer is option (c).

Hope it helps :)