A teacher collects a total of 17 mobile phones and iPads before a group of students heads off on a bushwalk. From a second group of students, 40 phones and iPads are collected. The second group had twice the number of phones and 3 times the number of iPads than the first group. How many phones and iPads did the first group have?

Step-by-step explanation:

216 boys

450 students: 20% girls, 80% boys

450*20%=90 girls

450*80%=360 boys

Students having mobile phones: 40% (OF THE 90) girls, 60% (OF THE 360) boys

90*40%=36 girls

360*60%=216 boys

[We honestly don't need to care about the girls without mobile phones as they are only asking how many boys have mobile phones]