Let cost of 1 part of sand be Rs x
Required = 3 parts , hence cost =Rs 3x
Let cost of 1 part of cement be Rs y
Required = 1 part , hence cost = Rs y
But cost of sand and cement are in a ratio 1:2, which means cost of cement is 2 times that of sand
Thus, y = 2x
Total cost = Rs1000
Thus, 3x+ 2x = 1000
5x = 1000
x= 200
Thus, cost of sand = Rs 200
Cost of cement = 2x
= 2(200)
= Rs 400.