Exercise: 3. Find the probability.
1. Picking a red marble from a jar containing 1 blue marble, 2 red marbles, and 3 green marbles.
2. Selecting a multiple of 2 from the numbers 1 - 10.
3. Rolling a 2 on a dice.
4. Rolling factors of 12 on a dice.
5. Rolling multiples of 3 on a dice.
Answer (2)
The probabilities for the scenarios are: 1) Picking a red marble: 3 1 ; 2) Selecting a multiple of 2: 2 1 ; 3) Rolling a 2: 6 1 ; 4) Rolling factors of 12: 6 5 ; 5) Rolling multiples of 3: 3 1 .
;
a probability is what's the ratio of desired cases vs. totally possible cases.
we have in total 1 blue + 2 red + 3 green = 6 marbles.
the desired cases are the 2 red marbles.
so, the probability is
2/6 = 1/3
total numbers : 10
multiples of 2 : 2, 4, 6, 8, 10 (5 cases)
so, the probability is
5/10 = 1/2
total possible results when rolling a die : 6 (1 ... 6).
there is only 1 way to roll a 2.
so, the probability is
1/6
total possible results when rolling a die : 6 (1 ...6).
factors of 12 : 1, 2, 3, 4, 6, 12 (6 cases). but 12 is not a possible result. that leaves us with 5 desired cases (1, 2, 3, 4, 6).
so, the probability is
5/6
total possible results when rolling a die : 6 (1 ...6).
multiples of 3 on a die : 3, 6 (2 cases).
so, the probability is
2/6 = 1/3 ;
