Question

Jonathan’s class has 30 boys. Of the students in his class, 60% are girls. How many girls are in Jonathan’s class?

Answer 1

45 girls

Explanation:

• Remark
• There are only 2 choices for gender. So if the class is 60% girls, the there must be 100 - 60 = 40% for the boys.
• But we are told that the boys are 30 in number.
• Let x = the total number of students.

Solution

• 40/100 * x = 30 Change the % to a decimal
• 0.4 x = 30 Divide both sides by 0.4
• 0.4 x / 0.4 = 30 / 0.4 Do the division
• x = 30/0.4
• x = 75 students in total

Formula

Total of Boys and Girls = Number of boys + number of girls.

Givens

• Total = 75
• Number of boys = 30

Solution II

• 75 = x + 30 Subtract 30 from each side
• 75 - 30 = x +30 - 30
• 45 = x
• There are 45 girls in the class.