SETS F1

 

In a certain school, 160 students take either Chemistry or biology. 140 take chemistry and 100 take both subjects. Find those who take biology only.

 

Solution

 

In most cases, OR stands for union whereas AND/BOTH, stands for intersection.

 

Let Chemistry = n(C), Biology = n(B).

 

n(C)= 140 ,

n(B)= ?

n(CuB) = 160,

n(CnB)= 100

 

 

Solution

 

n(CuB) = n(C) + n(B) - n(CnB)

 

160  =  140 + n(B)  – 100

 

160  =  n(B) + 40

 

160 - 40  =  n(B)

 

n(B)= 120

 

physics only = n(B) – n(CnB)

 

                    = 140 – 100

 

                    = 40 

 

 

Hence those taking only biology are 40.    

 

TRY THIS………….

 

In a certain school, 196 students take either Chemistry or French. 150 take chemistry and 110 take both subjects. Find those who take French only.