Ravi is making a mixture of sand, cement and water. He adds 6 kg of cement and 4
litres of water to every 10 kg of sand.
Which of these statements is not correct?
1) The water is 20 % of the mixture.
2) The ratio of sand to cement to water is 5:2:3.
3) To make 30 kg of mixture, Ravi needs 9 kg of cement.
4) If he uses 4.5 kg of cement, then he needs 3 L of water.

Question

Ravi is making a mixture of sand, cement and water. He adds 6 kg of cement and 4 
litres of water to every 10 kg of sand. 
          Which of these statements is not correct?
1) The water is 20 % of the mixture.
2) The ratio of sand to cement to water is 5:2:3.
3) To make 30 kg of mixture, Ravi needs 9 kg of cement.
4) If he uses 4.5 kg of cement, then he needs 3 L of water.

whpalmer4 · Answer

1 l of water is 1 kg

6kg cement + 4kg water + 10kg of sand makes 20kg of mixture

4kg water/20kg mixture = 1/5 = 0.2 = 20%

10 kg sand  : 6 kg cement : 4 kg water : factor out common factor of 2 gives 5:3:2

to make 30 kg of mixture, he need 6 kg/20*30 = 9 kg of cement

if he uses 4.5 kg of cement, he needs 4.5*2/3 = 3 kg = 3l of water

So the ratio of sand to cement to water answer is the incorrect statement.