SETS 4

In a certain school, 186 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) = 186,

n(CnP)= 100

Solution

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

186  =  130 + n(P)  – 100

186  =  n(P) + 30

186 - 30  =  n(P)

n(P)= 156

physics only = n(P) – n(CnP)

                         = 156 – 100

                         = 56 

Hence those taking only physics are 56.       

TRY THIS.....................................

In a certain school, 186 students take either Chemistry or physics. 134 take chemistry and 110 take both subjects. Find those who take Chemistry only.