Question

Dave is a builder. Yesterday he made mortar mix. He used 24kg of sand and 5kg of cement. Today he needs to make the same type of mortar mix, but he will use 36kg of sand. How much cement does he need?

Answer 1

7.5 kg

Explanation:

Ratio of sand to cement = 24kg : 5kg

Today he needs to make the same type of mortar mix, but he will use 36kg of sand.

Let

x = quantity of cement used

Ratio of sand to cement = 36 kg : x kg

Equate both ratios

24 kg : 5 kg = 36 kg : x kg

24/5 = 36/x

Cross product

24 * x = 5 * 36

24x = 180

x = 180/24

x = 7.5

x = quantity of cement used = 7.5 kg