Question

A person forgets two digits of user id for a website. he remembers that two digits are odd. what is the probability of him typing the correct last digits by randomly typing 2 odd digits?

Answer 1

Answer:

1/25

Step-by-step explanation:

The odd digits are 1,3,5,7,9 i.e., we have 5 chances .

And two digits can be same .

So probability is (1/5)*(1/5)=1/25.

Answer 2

Given,

The last two digits of an ID are odd.

To find,

The probability that on typing 2 odd digits randomly, the ID will be correct.

Solution,

Firstly, all the odd digits we have are 1, 3, 5, 7, and 9.

So, we have 5 odd numbers.

The probability of getting one digit correct will be,

$P=\frac{1}{5}$

Similarly, 2nd digit is also odd, so the probability of getting the 2nd digit correct will also be the same, that is,

$P=\frac{1}{5}$

Now to make sure that the ID is correct both the digits must be odd.

So, the probability of getting 1st digit AND 2nd digit odd will be,

$P=\frac{1}{5}\times \frac{1}{5}$

⇒ $P=\frac{1}{25}$

Therefore, the probability that the last 2 digits are correctly typed is $\frac{1}{25}.$