mabey you could help

i am trying to figure out how to count by multiples of 5, 10, 25, with the 7490, used with the 7447 BCD to seven seg.

Maybe you could make a bistable with an output for a No 5
and an output for a No 0,
on the lsd,
then run the counter from it
to run the rest as normal.

Best of luck with it, John