Question

Mark is making concrete.
Concrete is made by mixing cement, sand and gravel in the ratio 1:2:3.
Mark wants to make 300kg of concrete.
(a) How much cement does Mark need?
(b) How much sand does Mark need?
(c) How much gravel does Mark need?

Answer 1

1st value = 1st terms / sum of terms * total

so, cement needed = 1 / 1+2+3  *300  

                                  = 1/6 *300

                                  = 50kgs

2nd value = 2nd term /sum of terms * total

so, sand needed = 2 / 1+2+3 *300

                             = 2 / 6 *300

                             = 100kgs

now gravel needed is easy, 300 - (50+100) = 150