An urn contains 10 balls, numbered from 1 to 10. If 2 balls are selected at random with replacement from the urn, what is the probability P that the sum of the 2 numbers on the balls will be even? Select
A) 25%	B) 37.5%	C) 50%	D) 62.5%	E) 75%
Correct Answer: C   Since there are 5 even numbered balls and 5 odd numbered balls, the probability of selecting either an even or an odd is 5/10= 1/2. In order for the sum of the numbers on the two balls to be even, either both numbers must be even or both numbers must be odd; one even and one odd number would add to an odd number. The probability of selecting two even numbers is:   1/2 * 1/2= 1/4   The probability of selecting two odd numbers is also:   1/2 * 1/2= 1/4   Adding both probabilities gives P=1/4+1/4= 1/2 , or 50%, as the probability that the sum of the numbers will be even. Thus, the correct answer is (50%).
<result>C</result>
An urn contains 10 balls, numbered from 1 to 10. If 2 balls are selected at random with replacement from the urn, what is the probability P that the sum of the 2 numbers on the balls will be even?