# Basic probability

### Do you have questions about Basic probability?

How many two-digit numbers can be formed from the numbers 1,2,3,4 is repetirion is allowed

Krishna Laxman
Mathematics Trainer and Educational consultant

Two digit even number :  A numbers between 10 and 99 (including both) and one's digit should be even.

In our case ,the ten's digits can be filled in 5 ways and the one's digit can be filled in 2 ways

so totally $5\cdot2$ = 10 .

There are five spaces to be filled using the letters, R, E, A, C and T. The first letter can be filled in 5 ways. The second letter can be filled in 4 ways (since one of them is already used up in the first letter). The third letter can be filled i... (More)

The unit's place of the 2-digit number can be filled in 2 ways (2 or 4). The ten's place of the 2-digit number can be filled in 5 ways (1,2, 3, 4 or 5) since repetition is allowed. So the number of two-digit even numbers that can be formed with rep... (More)