Ratio about concrete

Your Question was wrong, what I am understand is M20 concrete 20mm metal is used.
m20- volumetric ratio - 1: 1.5 : 3

metal - 0.92 m3
sand - 0.46 m3
cement -0.31m3-441kgs in design mix 240kgs in moderate condition

For 1m3 of solid concrete the dry concrete mix should be 1.52m3.
so 1.52/(1+1.5+3) will give u the proportion for one part which is .267
therefore for cement .276m3
for sand .414m3
for coarse aggregate .818m3

I can understand your answer you asking about M20 CONCRETE .
CALCULATION:
Coefficient Method is actually M20 ratio is for Nominal mix 1:1.5:3
1:cement,
1.5:sand,
3:coarse aggregate,
For 1 cum concrete preparation required 0.46 cum of sand &0.92cum coarse aggregate and then 1/1.5(sand)x0.46x1440(cement Wt/1cum)=441.6kgs (or)441.6/50kgs(1bag of cem.)=8.83bags.

The total volume of materials needed for getting 1cum of concrete is 1.5cum.
The mix prop for M20 is 1:1.5:3.
So let a be the qty of cement,
then a+1.5a+3a=1.5
5.5a=1.5
a=0.27
so cement=0.27cum,sand=o.41cum,gravel=0.81cum.
This is more descriptive way to understand,the way of cal.the qnty.

The answers above not correct .. when we use that equation x+1.5+... = 1

we have to multiply by 0.7 as compaction factor so it will be

.7 ( x+1.5x + ... ) = 1

then get x the weight of each one