Question

What is the amount of dry matter in 100 kg rice having 100% moisture content on d.b. (dry basis)?

• A. 90 kg
• B. 50 kg
• C. 70 kg
• D. 85 kg

Hint:

When moisture content on dry basis is exactly \(100\%\), it means the weight of water is equal to the weight of dry matter.
Therefore, each component accounts for exactly half of the total weight (\(50 \text{ kg}\) each).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Moisture content can be expressed on a wet basis (w.b.) or dry basis (d.b.).
Dry basis moisture content is defined relative to the mass of dry matter, rather than the total mass of the product.

Step 2: Key Formula or Approach:
The moisture content on a dry basis (\(M_{db}\)) is given by: \[ M_{db} = \frac{W_w}{W_d} \times 100 \% \] where \(W_w\) is the mass of water, and \(W_d\) is the mass of dry matter.
The total mass of the sample (\(W_t\)) is the sum of the water mass and dry matter mass: \[ W_t = W_w + W_d \]

Step 3: Detailed Explanation:
Given:
Total mass, \(W_t = 100 \text{ kg}\)
Moisture content on dry basis, \(M_{db} = 100\%\)
Using the moisture content formula: \[ 100\% = \frac{W_w}{W_d} \times 100\% \implies \frac{W_w}{W_d} = 1 \implies W_w = W_d \] Now, substitute \(W_w = W_d\) into the total mass equation: \[ W_t = W_d + W_d = 2 W_d \] \[ 100 \text{ kg} = 2 W_d \] \[ W_d = 50 \text{ kg} \] Thus, the amount of dry matter in the rice is 50 kg.

Step 4: Final Answer:
The amount of dry matter is 50 kg.