Question

Shaun needs to make mortar for brick laying. It is made in the ratio 7:3 of sand to cement. If 210 kg of sand is used, how much cement is needed

Answer 1

Step 1: Assign variable for the unknown that we need to find.

Let x be the amount of cement needed.

Step 2: Set up a proportion based on the given information

Sand to Cement $= 7:3 = 210:x$

Step 3: Solve the proportion to find the value of x

$\frac{7}{3} =\frac{210}{x}\; [Cross\; multiplying\; on\; both\; sides]\\\\ 7\cdot x= 3\cdot 210\\ \\ 7x=630\; \; [Dividing\; by\; 7\; on\; both\; sides]\\ \\ \frac{7x}{7}=\frac{630}{7} \; [Simplifying\; the\; fraction\; on\; both\; sides]\\ \\ x=90$

Conclusion:

90 kg of Cement is needed !