Yes, 2/5 has a denominator of 5, 1/3 having a denominator of 3, and 4/15 has a denominator of 15. 3 and 5 are factors of 15, so 3 times 5 = 15, 5 times 3 = 15 15 times 1 = 15. What you do the denominator, you must do to the numerator, so 1 times 5 = 5(final fraction is 5/15), 2 times 3 = 6(final fraction is 6/15) and the 4/15 stays the same. 5 + 6 + 4 = 15, final answer is 15/15, that's the entire bag, and she could have a 4/15 chance of pulling out a Perfect Pitch.