Question

The probability that it rains tomorrow is 0.35. Work out the probability that it does not rain tomorrow.

Answer 1

We will discuss that the sum of probability of an event happening and an event not happening is 1. We will then put in the given value and find the required answer.

Complete step-by-step solution:
Let us say we have an event E and the probability of this event happening be P (E).
Now, we know that P (E) + P (E’) = 1.
Now, if we take the event E to be the event that it rains tomorrow.
Then we have P (E) = 0.35
Let us put this in the above mentioned formula. We will then obtain:-
$\Rightarrow$0.35+ P (E’) = 1
Taking the 0.35 from addition in the left hand side to subtraction in the right hand side, we will then obtain:-
$\Rightarrow$ P (E’) = 1 - 0.35
Simplifying the calculations on the right hand side of the above expression, we will then obtain:-
$\Rightarrow$ P (E’) = 0.65

Hence, the probability that it does not rain tomorrow is 0.65.

Note: The students must note that there are only two possibilities for an event, either it will happen or not. So, if there is some probability of it happening, since the total probability is 1. The probability of it not happening will be definitely the difference of one and the probability of it happening. Thus, we get the required formula of P (E) + P (E’) = 1.
The students must notice the fact that: probability is like the possibility percentage of an event divided by 100. For example: If it has 40% probability that I will be getting a snack that means, I have 0.4 probability that I will get a snack and thus have 0.6 probability that I would not be getting a snack.