Q.133 Botany ⭐ 360° Option Elimination Active

NEET 2026 Botany Question 133 Solution

Topic: Plant Growth and Development · Official NTA Booklet Code 50

Question

Length of the stem at time O is 20 cm. The arithmetic growth rate is 30 cm per day. What is the length of the stem at the end of the 7' day?

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Verified Against NTA Final Answer Key

Option (3) : 230 cm

📚 Plant Growth and Development Easy

📋 Given Parameters & Problem Setup

Initial Length (L₀) 20 cm at time t = 0

Arithmetic Growth Rate (r) 30 cm/day

Growth Period (t) 7 days

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The 30-Second Exam Hall Shortcut: ⚡ Arithmetic Growth Formula

⏱️ Save ~40 seconds

L_t = L₀ + rt -> 20 + (30 × 7) = 230 cm!

1 Recall the linear arithmetic growth formula: L_t = L₀ + r × t.

2 Plug in given values: L₀ = 20 cm, r = 30 cm/day, t = 7 days.

3 Multiply rate by time: 30 × 7 = 210 cm.

4 Add initial length: 20 + 210 = 230 cm.

5 Option (3) is 230 cm. Done in 5 seconds!

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Why You Can 100% Trust This Shortcut: NCERT Biology · Plant Growth and Development (Arithmetic Growth Formula: L_t = L₀ + rt).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Understand Arithmetic Growth Kinetics

In arithmetic growth, following mitotic cell division, only one daughter cell continues to divide while the other differentiates and matures. This produces a constant linear elongation over time, mathematically expressed by a straight line graph ( $y = mx + c$ ).

L_t = L_0 + rt

• L_t = Length at time t.
• L_0 = Initial length at time zero.
• r = Growth rate / elongation per unit time.
• t = Time elapsed.

Step 2

Substitute the Given Numerical Values

Given: $L_0 = 20\text{ cm}$ , $r = 30\text{ cm/day}$ , and $t = 7\text{ days}$ .

L_7 = 20 + (30 \times 7)

• Length added due to growth = 30 cm/day × 7 days = 210 cm.

Step 3

Calculate Final Length

Add the growth increment to the initial stem length:

L_7 = 20 + 210 = 230\text{ cm}

• Looking at options: (1) 50 cm, (2) 170 cm, (3) 230 cm, (4) 460 cm.
• Option (3) is 230 cm.

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360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Adds 20 + 30 for only 1 day of growth ( $t = 1$ ).

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Student Fallacy (Why candidates pick this trap): Ignoring the 7-day duration.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Subtracts initial length (210 - 20 = 190) or applies incorrect arithmetic.

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Student Fallacy (Why candidates pick this trap): Calculation blunder.

3 C

✓ 100% Correct

Verdict & Scientific Reason:

100% mathematically and conceptually accurate: $20 + (30 \times 7) = 230\text{ cm}$ .

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Why this is airtight: None; flawless linear kinetics.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Doubled the correct answer or misapplied geometric growth.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing arithmetic growth with exponential geometric growth.

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NTA Trap Alert: Forgetting to Add Initial Length (L₀)

Students calculate $30 \times 7 = 210\text{ cm}$ and either hunt for 210 or misread options, forgetting that the plant ALREADY measured 20 cm at $t = 0$ .

🛡️ How to avoid the -1 mark: Always use the complete equation: Final Length = Initial + Added.

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Core NEET Syllabus Standard

NEET Biology Core Syllabus · Plant Growth and Development Standard Benchmark

Core Scientific Principle Tested:

"Arithmetic growth is expressed mathematically as $L_t = L_0 + rt$ , plotting a linear curve with slope equal to growth rate r."

Syllabus Focus: Growth Rates - Arithmetic Growth

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Linear stem adds every day: start at twenty, add thirty times seven on the way!

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NEET 2026 Botany Question 133 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Arithmetic Growth Formula

Step-by-Step Rigorous Workflow & Mathematical Proof

Understand Arithmetic Growth Kinetics

Substitute the Given Numerical Values

Calculate Final Length

360° Option Elimination Engine Key Feature

NTA Trap Alert: Forgetting to Add Initial Length (L₀)

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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