u can take 0cm3 water, 10 cm3 salt , <the percentage conc is identical cuz its = (10/100) * (salt/water)>
th last column is simplt dividin by 2
then take 7.5water & 2.5 salt
then 2.5 water n 7.5 salt
then 2.5 water n 7.5 salt
there u go the readings are equally spaced + 3 readings are enough (i guess)
i wrote this in a hurry so if am not clear pls let me no