SOLUTION: the ratio of boys to all students in sam middle school is 2:5. there are 123 girls in the school. how many boys in the school?

Question 271565: the ratio of boys to all students in sam middle school is 2:5. there are 123 girls in the school. how many boys in the school?
Found 2 solutions by edjones, andriana121:
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
Let y=number of boys.
y/(123+y)=2/5 Proportion
5y=246+2y multiply each side by 5(123+y) to eliminate fractions.
3y=246
y=82
.
Ed
Answer by andriana121(7) (Show Source): You can put this solution on YOUR website!
Since the ratio of boys is 2:5, then the ratio of girls is 3:5.
To find out how many boys are in the class, you first need to figure out how many students there are.
To figure out how many students there are you need to set up a proportion. You should have this:
Mulitply 123 and 5 to get 615, then divide by 3 to get 205.
x=205
There are 205 students in all.
If there are 123 girls in the class, and 205 students in all, subtract girls from the students to find out how many boys are in the class.
205-123=82.
Therefore, there are 82 boys in the class.
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