P6 Math: Flour and Sugar

Shalih bought some bags of flour and sugar with the mass and prices shown below. The total mass of the flour is twice the total mass of the sugar. He paid a total amount of $127.20. Find the total mass of the flour and sugar bought by Shalih.

In this type of question there are two units involved, mass and price.

Total mass of flour = 2u

Total mass of sugar = u

Number of flour bags bought = f

Number of sugar bags bought = s

So,

2u = 0.7f and u= 0.2s (mass equations)

127.20 = 1.8f + 2s (price equation)

Solve the mass equation:

2u = 0.7f and 2u = 2 x 0.2s = 0.4s 

--> s : f = 7 : 4

Substitute to the price equation:

127.20 = 1.8f + 2 x (7/4f) = 5.3f --> f = 127.20 / 5.3 =  24

There were 24 flour bags.

s = (7/4)f = 42 

There were 42 sugar bags.

Total mass = (24 x 0.7) + (42 x 0.2) = 25.2 kg