Question

In 32 kg of a mixture of sand and gravel,
25% is sand. How many kg of sand must
be added to produce a mixture which is
30% gravel?​

Answer 1

Answer:

31.8 kg of sand to be added to the mixture

Step-by-step explanation:

Total mass of the mixture = 32 kg

Percentage of sand = 25%

Therefore:

Percentage of sand = 25%

Percentage of gravel = 100 - 25 = 75%

Find the ratio of sand to gravel:

sand : gravel = 25 : 75

Dividing by 25 through:

sand : gravel = 2 : 3

Find the composite of sand and gravel:

2 + 3 = 5 units

5 units = 32 kg

1 unit = 6.4 kg

sand = 2 units = 2 x 6.4 = 13 kg

gravel = 3 units = 3 x 6.4 = 19.2kg

Find the amount of sands to make 30% of the mixture gravel:

30% = 19.2kg

1% = 19.2 ÷ 30 = 0.54 kg

70% = 0.54 x 70 = 44.8 kg

Find the amount of sand to add:

original = 13kg

amount of sand needed = 44.8 kg

amount of sand to add = 44.8 - 13 = 31.8kg