The mean (average) height of a group of children would be increased by 6 cm if 12 of the children in the group were each 8 cm taller. How many children are in the group?

Let the number of children==C Let the mean height of all children==100 cm

100C==sum of the heights of all kids

[100C + (12*8)] / C ==100 + 6, solve for C

C==16 children