Question

The Probability of guessing the correct answer to a certain test question is x/12 . If the Probability of not guessing the correct answer to this question is 2/3 , then x = ___________.

Answer 1

Given :

The Probability of guessing the correct answer to a certain test question is x/12

Probability of not guessing the correct answer to this question is 2/3

To Find :

Value of x

Solution :

Now

We know that sum of probability of occurrence of an event and probability of non occurrence of an event is 1.

If E is an event of occurrence and E' is its complementary then

P(E) + P(E') = 1 ... (1)

where

P(E) = Probability of guessing the correct answer

and

P(E') = Probability of guessing the incorrect answer

Putting values of P(E) and P(E') in equation 1 we get

$\frac{x}{12} + \frac{2}{3} = 1$

$\frac{x + 8}{12} = 1$

$x + 8 = 12$

$x = 4$

Hence, 4 is the required value of x.

Answer 2

A N S W E R :

• The value of x is 4

Given :

• The Probability of guessing the correct answer to certain test question is x/12

To find :

• Find the value of x ?

Solution :

• The sum of all probabilities of all possible outcomes of experiment = 2/3

P(Event) + P(not a Event) = 1

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

=> x/12 + 2/3 = 1

=> x/12 = 1 - 1/3

=> x/12 = (3 - 2)/3

=> x/12 = 1/3

=> 3x = 12

=> x = 12/3

=> x = 4

Hence,

• The value of x is 4