waecmaths question:
M and N are two subset of the universal sets (U). if n(U) =48, n(M) = 20, n(N) =30 and $n(M\cup N)=40$, find $n(M\cap N)'$
Option A:
18
Option B:
20
Option C:
30
Option D:
38
waecmaths solution:
$\begin{align} & n(M\cup N)=n(M)+n(N)-n(M\cap N) \\ & 40=20+30-n(M\cap N) \\ & n(M\cap N)=50-40=10 \\ & n(M\cap N)'=n(U)-n(M\cap N) \\ & n(M\cap N)'=48-10=38 \\\end{align}$
maths year:
maths topics: