Question

On a single roll of two number cubes, what is the probability of rolling doubles given that the sum is 6

Answer 1

Answer:

1/6

Step-by-step explanation:

We can make a Punnett square to find number of favourable outcome

so

            cube1

         +

cube2    1          2          3        4          5         6

1            2         3           4        5          6        7      

2            3         4           5        6          7         8    

3            4          5         6        7         8         9

4           5          6          7         8         9         10

5         6           7          8         9        10         11

6           7           8          9         10        11         12

The probability of rolling doubles given that the sum is 6

favourable outcome / number of outcome

 6 / 36

  1 / 6

Answer 2

Answer:

1/5

Step-by-step explanation:

P(A/B)= P(A and B)/ P(B)

Sum of 6:     5/36

(1,5)---(5,1)---(2,4)---(4,2)---(3,3)

Probability of rolling doubles:      6/36

(1,1)---(2,2)---(3,3)---(4,4)---(5,5)---(6,6)

Out of these two "requirements" only one thing overlaps: (3,3)

Therefore:

P(A/B)= (1/36) ÷ (5/36)= 1/5