Question

The average height of 30 girls in a group of 40 is 160 cm and that of the remaining girls is 156 cm. Find the average height of the whole group

Answer 1

avg height=(sum of height of 30 girls/30)=160 {given}
sum of height of 30 girls = avg height x 30 = 160 x 30 = 4800

avg height=(sum of height of 10 girls/ 10)=156 {given}
sum of height of 10 girls = avg height x 10 = 156 x 10 = 1560

avg height of whole class
=(sum of height of 30 girls + sum of height of 10 girls)/40
=(4800+1560)/40
=6360/40
=159m

so the avg height of the whole class is 159m