Question

a class has 60 boys and 40 girls. The probability of a selecting a boy from the class is ?​

Answer 1

Answer:

60

——

40

Step-by-step explanation:

20% more probability than girls.

Answer 2

Answer:

Probability both are boys = (60/100)*(59/99) = 0.3576= 35.76%

Probability both are girls = (40/100)*(39/99) = 0.1576 = 15.76%

Probability one boy and one girl = (60/100)(40/99) + (40/100)(60/99) = 2(60/100)(40/99) = 0.4848 = 48.48%

On this last calculation, we have 2 options, either we get a boy first and a girl second, or vice-versa. That’s why there are two terms. The reason why it simplifies to 2 times one of the terms, is because both terms are equal. This is due to the properties of multiplying fractions. When you multiply the fractions, you get:

(60/100)(40/99) = (60*40)/100*99) AND (40/100)(60/99) = (40*60)/(100*99) which is the exact same as the 1st one. Therefore when adding them together, it comes out to twice either of the terms