To determine the probability that the sum of the two upward faces will be 7 when throwing two unbiased dice, we follow these steps:
Step 1: Identify the total number of possible outcomes.
Each die has 6 sides (numbered 1 to 6). When two dice are thrown, the total number of possible outcomes is the product of the number of outcomes for each die.
Total number of outcomes = Number of sides on Die 1 \(\times\) Number of sides on Die 2
Total number of outcomes = \(6 \times 6 = 36\)
Step 2: Identify the number of favorable outcomes (where the sum of the faces is 7).
We list all the combinations of two dice that add up to 7:
(1, 6) - Die 1 shows 1, Die 2 shows 6
(2, 5) - Die 1 shows 2, Die 2 shows 5
(3, 4) - Die 1 shows 3, Die 2 shows 4
(4, 3) - Die 1 shows 4, Die 2 shows 3
(5, 2) - Die 1 shows 5, Die 2 shows 2
(6, 1) - Die 1 shows 6, Die 2 shows 1
There are 6 favorable outcomes.
Step 3: Calculate the probability.
The probability of an event is calculated by dividing the number of favorable outcomes by the total number of possible outcomes.
Probability (P) = (Number of favorable outcomes) / (Total number of possible outcomes)
P(sum is 7) = \(6 / 36\)
P(sum is 7) = \(1 / 6\)
Therefore, the probability that the sum of the two upward faces will be 7 is \(\frac{1}{6}\).