C.I	0-10	10-20	20-30	30-40	40-50	50-60
frequency	4	6	10	18	9	3

Solution:

C.I	$x_{i}$	$f_{i}$	$f_{I}x_{i}$
10-20	15	4	60
20-30	25	6	150
30-40	35	10	350
40-50	45	18	810
50-60	55	9	495
60-70	65	3	195
		50	2060

$\operatorname{Mean} \overline{x}=\frac{\sum f_{i} x_{i}}{N}$

$\therefore \overline{x}=\frac{2060}{50}$

$\therefore \overline{x}=41.2$