SOLUTION: 30% of the pupils in a class are boys.There are 21 girls.How many pupils are there in the class inall?

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Question 975154: 30% of the pupils in a class are boys.There are 21 girls.How many pupils are there in the class inall?
Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
let x be the total number of students
we are given that 30% of all students are boys, so 1 - 0.30 = 0.70 and 70% of all students are girls, then
0.70x = 21
x = 21 / 0.70 = 30
there are 30 students in the class