We can use a weighted average here =
[ sum of freq* mipoint ] / [sum of freq ] \
[ (1*5) + (4*15) + (7 * 25) + (2 * 35) + (3 * 45) + (3 * 55)
_______________________________________________
[ 1 + 4 + 7 + 2 + 3 + 3 ]
[ 610 ]
______
20
30.5 cm = mean height of the plant
