increasing by a simple %

a ppt is here

end numbers have a 0 or 5 as the last digit

both start and end numbers have a common factor

they are all 4k , 5k

the start numbers might better be chosen to be of the form 20k

then the end numbers are 23k

with multiples of 10 as start numbers the end numbers are 11.5k

being given 10  ,  11.5 helps...