Problema Solution
A box contains five numbered ping-pong balls. One ball has the number 1 painted on it, one ball has 3, two of the balls are labeled with a 6, and one ball has an 8. The balls are picked from the box one at a time without replacement and placed in the order they are drawn, from left to right, to create a five-digit number. What is the probability that the five digit number is a composite number (not prime)?
Answer provided by our tutors
A number is divisible by 3 if the sum of its digits is divisible by 3.
Since 1 + 3 + 6 + 6 + 8 = 24 all the numbers formed from the digits 1, 3, 6, 6 and 8 are divisible by 3
The probability that the five digit number is a composite number (not prime) is 1 or 100%.