cumulative run rate is not average of averages... suppouse u make 300 one day so ave is 6... next day u make 250 all out in 40 overs ave is 6.25... then net runrate is NOT 6.125... it will be 5.50 because in the second match no of overs will be taken as 50...
otherwise all teams would try to make 300 all out in 30 overs, in that case nrr would be 10 which wud be directly averaged... not like that
