Question

There are 300 pupils in a stadium. 40% of them were boys. 60 more boys entered the stadium. What percentage of the pupils in the stadium are boys now? 

1. 20%
2. 30%
3. 50%
4. 60%​

Answer 1

Question

There are 300 pupils in a stadium. 40% of them were boys. 60 more boys entered the stadium. What percentage of the pupils in the stadium are boys now?  

1. 20%

2. 30%

3. 50%

4. 60%

Answer

Simply set up a systems of equations.

let x=number of boys, and

let y=number of girls.

since there are 30 more boys than girls, we can say that y+30=x, or the amount of boys is equal to the number of girls plus thirty more.

We can also say that the total number of students in the class is 130, so x+y=130, or the number of girls plus the number of boys is equal to 130 students.

x+y=130

y+30=x

Because x is y+30, we can substitute the x in the first equation with y+30, so

x+y=130 is (y+30)+y=130 is y+y+30=130 is 2y+30=130

Subtract thirty from both sides, and you get 2y=100

Divide by two, and get y, or the number of girls, is equal to 50 students.

Looking back to the first equation, substitute 50 for y, and get;

x+y=130 is x+50=130 subtract 50 from both sides, you get x, or number of boys, is 80 students.

Answer 2

Answer:

pupils=300

boys=40%

400x300÷100

=120

pupils=300+60 more boys

=360

boys=120+60=180

180x100÷360

=50%