this is a part:part ratio. to answer the question, we need to change it into a part:whole ratio. to do this we add up the parts to equal 7. so the ratio of girls to students is 3:7. divide 238 (whole) by 7 (whole) to equal 34. now we multiply 34 by 3 for girls and by 4 for boys. girls: 102; boys: 136.