Find the mass, in kilograms, of cement needed to make the slab.

here are the solutions to the quiz questions:

Question 18:
m) Find the mass, in kilograms, of cement needed to make the slab.

Step 1: Determine the overall ratio of Ballast : Sand : Cement.
Given ratios:
Sand : Cement = 9 : 5
Ballast : Sand = 2 : 1
To combine these, make the 'sand' part consistent. Multiply the Ballast : Sand ratio by 9:
Ballast : Sand = $(2 \times 9) : (1 \times 9) = 18 : 9$
So, the combined ratio is Ballast : Sand : Cement = 18 : 9 : 5.

Step