Question

The mean weight of three gemstone is 20 grams .The weight of two of the stone are 15 grams and 17 grams what is the weight of the third stone

Answer 1

Mean weight =20

Let unknown weight be x

So,

(15+17+x)/3=20

=32+x=60

=x=60-32=28

The weight of the third stone is 28g