M25 Concrete Cement Sand Aggregate In Cum

What are the mix ratios for cement and sand , more water, cement or sand can be added if the mixture is too wet or dry below is an example of a sand to cement mix ratio recommendation from a cement manufacturer concrete - 1 part cement, 2 parts concreting sand and 3 parts 20 millimeter aggregate mortar - 1 part cement, 4 to 5 parts building sand.