WAEC - Mathematics (2001 - No. 4)
In a class of 80 students, every students studies Economics or Geography or both. If 65 students study Economics and 50 study Geography, how many study both subjects?
15
30
35
45
Explicación
Let c = no of students that offered both subjects
\(\therefore\) No of students offering Economics = 65 - c
No of students offering Geography = 50 - c
65 - c + c + 50 - c = 80
115 - c = 80
c = 35
35 students offer both Economics and Geography.