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Question 51
GATE BT 2026 • Q51
NAT • 2 Marks
Section 2: General Biotechnology
Biomolecules, enzyme kinetics
Subtopic: Fundamentals of Biomolecules, enzyme kinetics
Question Statement:
Consider the equation
dy
dx =
1
x
The value of the integral ∫ dy
2
1 using trapezoidal method and interval ℎ = 0.25
is ________. (rounded off to two decimal places)
Official Answer Key:
0.69 to 0.71
Step-by-Step Solution & Explanation
### **Step-by-Step Solution & Mathematical Derivation (GATE BT 2026 Q.51)**
**1. Governing Concept & Definition**:
- **Topic**: Numerical Methods & Trapezoidal Rule of Numerical Integration
- The composite trapezoidal rule for step size $h$ is:
$\int_a^b f(x)\,dx \approx \frac{h}{2} \left[ f(x_0) + 2\sum_{i=1}^{n-1} f(x_i) + f(x_n) \right]$
**2. Detailed Step-by-Step Calculation**:
- **Function**: $f(x) = \frac{1}{x}$ over $[1, 2]$ with $h = 0.25$.
- **Grid Points**:
- $x_0 = 1.00 \implies f(x_0) = 1.0000$
- $x_1 = 1.25 \implies f(x_1) = \frac{1}{1.25} = 0.8000$
- $x_2 = 1.50 \implies f(x_2) = \frac{1}{1.50} = 0.6667$
- $x_3 = 1.75 \implies f(x_3) = \frac{1}{1.75} = 0.5714$
- $x_4 = 2.00 \implies f(x_4) = \frac{1}{2.00} = 0.5000$
- **Trapezoidal Summation**:
$\text{Integral} \approx \frac{0.25}{2} [1.0000 + 2(0.8000 + 0.6667 + 0.5714) + 0.5000]$
$= 0.125 \times [1.0000 + 2(2.0381) + 0.5000] = 0.125 \times [1.5000 + 4.0762] = 0.125 \times 5.5762 \approx 0.6970$
**3. Final Answer**:
- **Calculated Value**: **0.70**
- **Official GATE Accepted Range**: **0.69 to 0.71**
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