SETS K2

 

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

 

Solution

 

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

 

Let Chemistry = n(C),

      physics = n(P).

 

n(C)=160 ,

n(P)=?

 

n(CuP)= 140,

n(CnP)=100

 

Now,the formula

 

n(CuP)= n(C) + n(P) – n(CnP)

 

140 =  160 + n(P)  – 100

 

140 =  160 – 100 + n(P) 

 

140 =  60+ n(P) 

 

140– 60  =  n(P)

 

n(P)=80

 

Hence those taking  physics are 80.  

 

TRY THIS………….

 

In a certain school, 185 students take either Chemistry or French. 160 take chemistry and 130 take both subjects. Find those who take French.