SETS 4

In a certain school, 140 students take either Chemistry or physics. 130 take chemistry and 100 take both subjects. Find those who take physics only.

Solution

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

Let Chemistry = n(C), physics = n(P).

n(C)= 130 ,

n(P)= ?

n(CuP) = 140,

n(CnP)= 100

Solution

n(CuP) = n(C) + n(P) - n(CnP)

140  =  130 + n(P)  – 100

140  =  n(P) + 30

140 - 30  =  n(P)

n(P)= 110

physics only = n(P) – n(CnP)

                    = 110 – 100

                    = 10 

Hence those taking only physics are 10.    

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 only.