SETS B7

In a certain school, 190 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) = 190,

n(CnP)= 100

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

190  =  130 + n(P)  – 100

190  =  n(P) + 30

190 - 30  =  n(P)

n(P)= 160

physics only = n(P) – n(CnP)

                         = 160 – 100

                         = 60 

Hence those taking only physics are 60.      

TRY THIS…..

In a certain school, 220 students take either Chemistry or physics. 133 take chemistry and 110 take both subjects. Find those who take physics only.