Thread: need help plz, counting

In a kindergarten class of 32 childern,15 have brothers,14 have sisters and 8 have neither sisters nor brothers.how many childers in this class have both brothers and sisters

Originally Posted by gracy

In a kindergarten class of 32 childern,15 have brothers,14 have sisters and 8 have neither sisters nor brothers.how many childers in this class have both brothers and sisters

Let a have brothers only, b have sisters only and c have brothers and sisters.

Then

a+b+c=32-8=24 ..(eq1)

also

a+c=15 ..(eq2)

and

b+c=14 ..(eq3)

Subtract eq2 from eq1 gives:

(a+b+c)-(a+b)=24-15,

so

c=9,

hence a=6, and b=5.

RonL