#13 Probability

Below there are sixteen numbers. Assuming that any three of the numbers may be drawn at random, what are the chances that three numbers will be drawn whose sum equals six?

1 2 3 1
2 3 1 2
3 1 2 3
1 2 3 1

alright 1 week has passed,

Hint #1 the percentage (preferable answer form)

is below 50 and above 10

Hint #2  the answer ( in %) is between 30 and 20

I guess nobody likes math problems, anyway its over

 no one got it, that is except for my dad who gets 100 points

inquire within for the answer

#12 The Golden Rings

You arrive at a hotel and have 3 sets of golden rings. The first set of rings has 4 rings, the second set has 2 rings and the third only has one ring. You cannot take these sets of rings apart, exchange them for a different form of currency, and the hotel clerk has no change. You want to stay at the hotel for 7 nights, and you have to pay one gold ring for each night that you stay. You cannot pay in advance, or all at once at the end of your stay. How do you pay for your 7 nights at the hotel?

#11 The Marbles

You are given a set of scales and 12 marbles. The scales are of the old balance variety. That is, a small dish hangs from each end of a rod that is balanced in the middle. The device enables you to conclude either that the contents of the dishes weigh the same or that the dish that falls lower has heavier contents than the other. The 12 marbles appear to be identical. In fact, 11 of them are identical, and one is of a different weight. Your task is to identify the unusual marble and discard it. You are allowed to use the scales three times if you wish, but no more. Note that the unusual marble may be heavier or lighter than the others. You are asked to both identify it and determine whether it is heavy or light

Hint#1 You may find the answer easier if you number the marbles and place them in 3 groups of 4

please take the time and explain your answer, make it as long as you need, this may be a little difficult but I think you can get it

#10 The Letter Series

what are the next letters in this series
O T T F F S S _ _ _