Answer to Question #281752 in Discrete Mathematics for Bala

Question

How many students are offering both biology and chemistry,if only 70 students are offering neither biology or chemistry.

Answer 1

QUESTION:

Out of 400 students in a final year of a senior secondary, 300 are offering Biology and 190 are offering Chemistry.

How many students are offering both Biology and Chemistry if 70 students are offering neither Biology nor Chemistry.

SOLUTION:

Let $n$ $=$ the number of students offering both Biology and Chemistry.

Biology student only$=(300-n)$

Chemistry student only$=(190-n)$

Neither Biology nor Chemistry$=70$

$\therefore n+(300-n)+(190-n)+70=400$

$560-n=400\\n=160$