SETS - 2

In a certain school, 196 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) = 196,

n(CnP)= 100

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

196  =  130 + n(P)  – 100

196  =  n(P) + 30

196 - 30  =  n(P)

n(P)= 166

physics only = n(P) – n(CnP)

                    = 166 – 100

                    = 66 

Hence those taking only physics are 66.      

TRY THIS…..

In a certain school, 220 students take either Chemistry or physics. 140 take chemistry and 110 take both subjects. Find those who take physics only.