James is making concrete using cement, sand and gravel in the ratio 1 : 2 : 3

James has:
63kg cement
112kg sand
210kg gravel
What is the maximum amount of concrete that James can make?

1 answer

To determine the maximum amount of concrete James can make in the ratio of 1:2:3 for cement, sand, and gravel, we first need to consider the quantities he has and how they fit into that ratio.

  1. Ratio Components:

    • For every 1 part of cement, he needs 2 parts of sand and 3 parts of gravel.
    • This means the total parts = \(1 + 2 + 3 = 6\) parts.
  2. Calculate the Required Amounts:

    • If \(x\) is the amount of cement in kg, then:
      • Amount of sand needed \(= 2x\)
      • Amount of gravel needed \(= 3x\)
  3. Set Up the Inequalities: We have the amounts of materials James possesses:

    • Cement: 63 kg
    • Sand: 112 kg
    • Gravel: 210 kg

    Based on the ratio:

    • For cement: \(x \leq 63\)
    • For sand: \(2x \leq 112 \Rightarrow x \leq \frac{112}{2} = 56\)
    • For gravel: \(3x \leq 210 \Rightarrow x \leq \frac{210}{3} = 70\)
  4. Find the Limiting Factor: The limiting quantity for \(x\) is the smallest value obtained:

    • From cement: \(x \leq 63\)
    • From sand: \(x \leq 56\)
    • From gravel: \(x \leq 70\)

    Therefore, the limiting ingredient is sand, giving \(x \leq 56\).

  5. Calculate the Maximum Amount of Concrete: The total amount of concrete can now be calculated using the ratio:

    • Total parts = \(6\) (from the ratio of 1:2:3)
    • Maximum \(x = 56\) kg (cement part)

    Total concrete made: \[ \text{Total concrete} = 6x = 6 \times 56 = 336 \text{ kg} \]

Thus, the maximum amount of concrete that James can make is 336 kg.