In a school there are 280 girls. The ratio of the number of boys to the number of girls is 9 : 7. Find the total number of students in the school.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 640
In the ratio 9 : 7 the girls are 7 parts and all the students are \(9+7=16\) parts. The number of girls gives the size of one part.
7 parts \(=280\), so 1 part \(=40\)
Boys \(=9\times40=360\)
Total \(=16\times40=640\)
There are 640 students in the school.