The number of ways of having 3 boys (B) and 2 girls (G) is the number of distinct arrangements of BBBGG. Therefore, the number of outcomes in the event is number of ways to have 3 boys and 2 girls . Each of the 5 children can be a boy or a girl. Using the Fundamental Counting Principle, the number of outcomes in the sample space is 2 ? 2 ? 2 ? 2 ? 2 = 32. Therefore, the probability of having 3 boys and 2 girls is
The probability that they will have 3 boys and 2 girls is 0.3125 or 31.25%. 

Read pages 156157 Example 3 in your textbook, Principles of Mathematics 12. Complete the Your Turn question on page 157 for more practice solving probability problems using reasoning. Click here to verify your answer . 
Some examples can be solved using combinations. Examples 3 and 4 explore this.
If the 4 coins total 25 cents, they must be 3 nickels and 1 dime.
Because the order in which the coins are selected does not matter, use combinations. The number of ways 3 nickels can be selected from 35 nickels is _{ 35 } C _{ 3 } . The number of ways 1 dime can be selected from 50 dimes is _{ 50 } C _{ 1 } . Using the Fundamental Counting Principle, the number of ways 3 nickels and 1 dime can be selected from the 85 coins in the jar is _{ 35 } C _{ 3 } ? _{ 50 } C _{ 1 } . The number of outcomes in the sample space is the number of ways 4 coins can be selected from the 85 in the jar, _{ 85 } C _{ 4 } .
The probability that the 4 coins total 25 cents is about 0.162 or 16.2%. 