Step 1: Read the question and note down the given information.

GIVEN: The total number of students in 10th class = 40

number of boys = 15

Number of girls = 25

Form the box only one name card has to be chosen.

Step 2: Calculate the probability that the card with the name of a girl.

NOTE: The number of all possible outcomes is 40

The number of outcomes favourable for a card with the name of a girl = 25

\therefore P (card with name of a girl) = P(Girl) = \frac{25}{40} = \frac{5}{8}

Step 3: Find the probability that the card with the name of a boy.

NOTE: The number of outcomes favourable for a card with the name of a boy = 15

\therefore , P(card with name of a boy) = P(Boy) = \frac{15}{40}= \frac{3}{8}

or

P(Boy) = 1 - P(not Boy) = 1 - P(Girl) = 1 - \frac{5}{8} = \frac{3}{8}