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There are four nickels and seven dimes in your pocket. One of the nickels and one of the dimes are Canadian. The others are US currency. You randomly select a coin from your pocket. It is a dime or is Canadian currency. Find the probability of this occurring.

A. [tex]$\frac{5}{7}$[/tex]
B. [tex]$\frac{8}{11}$[/tex]
C. [tex]$\frac{7}{12}$[/tex]
D. [tex]$\frac{7}{9}$[/tex]

Sagot :

To solve this problem, let's go through a detailed step-by-step solution.

1. Total Number of Coins:

First, calculate the total number of coins in your pocket. You have 4 nickels and 7 dimes.

[tex]\[ \text{Total Coins} = 4 (\text{nickels}) + 7 (\text{dimes}) = 11 \text{ coins} \][/tex]

2. Number of Dimes:

You are given that there are 7 dimes in total.

3. Number of Canadian Coins:

There is 1 Canadian nickel and 1 Canadian dime, so the total number of Canadian coins is:

[tex]\[ \text{Canadian Coins} = 1 (\text{nickel}) + 1 (\text{dime}) = 2 \text{ coins} \][/tex]

4. Calculate the Probability of Selecting a Dime:

The probability of selecting a dime is computed by dividing the number of dimes by the total number of coins.

[tex]\[ P(\text{Dime}) = \frac{\text{Number of Dimes}}{\text{Total Coins}} = \frac{7}{11} \][/tex]

5. Calculate the Probability of Selecting a Canadian Coin:

The probability of selecting a Canadian coin is computed by dividing the number of Canadian coins by the total number of coins.

[tex]\[ P(\text{Canadian}) = \frac{\text{Number of Canadian Coins}}{\text{Total Coins}} = \frac{2}{11} \][/tex]

6. Calculate the Probability of Selecting a Canadian Dime:

Since there is only 1 Canadian dime, the probability of selecting this specific coin is:

[tex]\[ P(\text{Canadian Dime}) = \frac{1}{11} \][/tex]

7. Combine the Probabilities:

We are interested in the probability that the selected coin is either a dime or a Canadian coin. We use the principle of inclusion-exclusion to combine these probabilities:

[tex]\[ \text{Probability} = P(\text{Dime}) + P(\text{Canadian}) - P(\text{Canadian Dime}) \][/tex]

Substituting the values calculated:

[tex]\[ \text{Probability} = \frac{7}{11} + \frac{2}{11} - \frac{1}{11} \][/tex]

Simplify the expression:

[tex]\[ \text{Probability} = \frac{7 + 2 - 1}{11} = \frac{8}{11} \][/tex]

The final probability that you will either select a dime or a Canadian coin is:

[tex]\[ \boxed{\frac{8}{11}} \][/tex]

So, the correct answer is B. [tex]\(\frac{8}{11}\)[/tex].