Answer:
1/4 parts of cement
Explanation:
Given :
3 parts of cement = 12 parts of sand
For each part of sand, let the part of cement used = x
Writing the relation in the form of cross multiplication :
3 = 12
x = 1
Cross multiply :
12x = 3
x = 3 / 12
x = 1/4
Hence, for each part of sand, 1/4 parts of cement is used.