Solving Proportions Examples Page 6

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A tricky example. Sometimes math problems like to throw in extra info to make you think.

The ratio of girls to boys in your class is 4:5. Assuming that this ratio is consistent throughout the school, approximately how many boys would be in a school of 525 students?
Ok, the tricky part with this problem is dealing with two different ratio set-ups. The first part of the problem talked about a ratio of girls to boys. The second part, however, asked about the ratio of boys to total students. Trying to solve the equation above would be like trying to herd bees into a beehive.
However, we can translate the first ratio into the same format as the second, which is boys: total. If there are 5 boys for every 4 girls, this would give a ratio of 5 boys to every 9 students (5 boys + 4 girls = 9 students).
Now, cross multiply:
Finally divide 2625 by the coefficient, 9: Again, since we’re estimating the number of boys, and having of a student is hard to imagine, we can round this number to the nearest whole number. So, there are approximately boys in your school. Sweet!