Respuesta :
The probability would be 5/6.
There are 6 ways we can roll two dice and have the first number be a 1:
1, 1
1, 2
1, 3
1, 4
1, 5
1, 6
Out of these, 5 possibilities give us a sum less than 7:
1, 1
1, 2
1, 3
1, 4
1, 5
Thus we have 5/6.
There are 6 ways we can roll two dice and have the first number be a 1:
1, 1
1, 2
1, 3
1, 4
1, 5
1, 6
Out of these, 5 possibilities give us a sum less than 7:
1, 1
1, 2
1, 3
1, 4
1, 5
Thus we have 5/6.
Answer: The correct option is (d) five over six.
Step-by-step explanation: Given that John rolls a number cube twice. We are to find the probability that the sum of the 2 rolls is less than 8 given that he first roll is a 1.
The sample space of an event of rolling a cube is
S = {1, 2, 3, 4, 5, 6}.
That is, n(S) = 6.
Now, let 'A' be the event that the sum of the two rolls is less than 7, then
A = {1, 2, 3, 4, 5}.
That is, n(A) = 5.
So, the probability of happening of event A is given by
[tex]P(A)=\dfrac{n(A)}{n(S)}=\dfrac{5}{6}.[/tex]
Thus, the required probability is five over six.
Option (d) is correct.
