Question 45703
A survey of 150 students showed that 90 were taking psychology, 75 were taking economics and 22 were taking neither. The number taking both was how many?
LET PEOPLE TAKING ONLY PSYCHOLOGY =P
LET PEOPLE TAKING ONLY ECONOMICS=E
LET PEOPLE TAKING BOTH =B
LET PEOPLE TAKING NEITHER =N
TOTAL = P+E+B+N=150...................1
P+E+B+22=150......................
P+E+B=150-22=128........................2
P+B=90.....................3
E+B=75....................4
EQN.3+EQN.4 GIVES
P+E+2B=90+75=165........................5
EQN.5-EQN.2 GIVES
B=165-128=37