There are 5 balls in the urn, on which the numbers 1, 2, 3, 4, 5 are written. Choose 2 balls at random.

There are 5 balls in the urn, on which the numbers 1, 2, 3, 4, 5 are written. Choose 2 balls at random. What is the probability that the sum of the numbers is seven?

The total number of outcomes when choosing 2 balls out of 5.
C (5,2) = 5! / (2! (5 – 2)!) = 4 5 / (1 2) = 10.
The number of favorable options when the sum of the numbers is 7 – m = 4; (3 + 4); (4 + 3); (2 + 5); (5 + 2).
The probability that the sum of the numbers is seven.
P = m / n = 4/10 = 0.4.
Answer: 0.4.