Maths * Henry is mixing concrete. To make concrete he needs to mix cement, sand and gravel in the ratio 4 : 3 : 1 by weight. Henry needs to make 120kg of concrete. He has 55kg of cement, 45kg of sand and 15kg of gravel. Which ingredient is Henry short of?

His 55 kg of cement is 5 kg short of the 60 kg he needs.

Step-by-step explanation:

Let r be a ratio useful in determining how much of each ingredient Henry needs:

4/8 of the mix is cement, 3/8 is sand and 1/8 is gravel.

4/8 of the total 120 kg must then be 60 kg made up of cement;

3/8 must then be 45 kg made up of sand; and

1/8 must then be 15 kg made up of gravel

His 55 kg of cement is 5 kg short of the 60 kg he needs.