as the density of water is 1. if we multiply the water
cement ratio with the cement being used , we will get the
amount of water. For example if water cement ratio is 0.45
and cement being used is 400 kg per cum, then the water
required will be 0.45x 400=180 litres per cum of concrete.

i really dont know pls mail me the correct answer with
calculations for 1:2:4 mix, 1;1.5:3mix, 1:4:8mix.including
volume of cement, sand ,aggregate.thank u.

From Water cement Chart,
First you get what type of cement you used & than comapire
with your target mean strength of Concrete from chart you
get W/C ratio, which helps you to get Qty of Sand &
Aggregate

Please go to
http://www.engineeringcivil.com/concrete-mix-design-as-per-
indian-standard-code.html?cp=7
After reading that
click on M-15 mix designs, M-20 etc to get the ratios.

Remember there are ratios based on weight (mass) and volume.
So go through the tables and write down what you want and
explain to the others whether the ratios are by volume or
mass.

From Water cement Chart,
First you get what is the range of compressive strength of
cement at 28 days you used from the quality Test
certificate or manufacturer Test certificate & than
comapare with your target mean strength of Concrete from
chart you
get W/C ratio