find the mean of the following distribution: x | 4 | 6 | 9 | 10 | 15 |
f | 5 | 10 | 10 | 7 | 8 |

xf = 20 + 60 + 90 + 70 + 120 = 360
f   = 5 + 10 + 10 + 7 + 8 = 40
Therefore mean = 360/40
                        =9 
Enjoyyy.... Thumbs up!!