Jambmaths question:
A bookseller sells Mathematics and English books. If 30 customers brought Mathematics books, 20 customers brought English books and 10 customers buy the two books, how many customers has he altogether?
Option A:
30
Option B:
40
Option C:
50
Option D:
60
Jamb Maths Solution:
$\begin{align} & n(M)=30 \\ & n(E)=20 \\ & n(M\cap E)=10 \\ & n(M\cap {{E}^{1}})=30-10=20 \\ & n({{M}^{1}}\cap E)=20-10=10 \\ & n(M\cup E)=n(M\cap {{E}^{1}})+n(M\cap {{E}^{1}})+(M\cap E) \\ & n(M\cup E)=20+10+10 \\ & n(M\cup E)=40 \\\end{align}$
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