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Class 10 Science • Chapter 15 • Energy Flow & Trophic Levels

📘 Numerical Practice

इस chapter के numericals मुख्य रूप से energy flow, 10% law और trophic levels पर आधारित हैं। पहले calculation खुद करें, फिर solution देखें।

10% Law E₂ = 10% of E₁
Percentage Form E₂ = 0.1 × E₁
Reverse Calculation E₁ = E₂ / 0.1
Multiple Levels Eₙ = E₀ × (0.1)ⁿ
🎯 Difficulty
20 TOTAL
4 EASY
8 HARD + VERY HARD
4 EXPERT
Numerical 1 – Producer to Herbivore
EASY
10% Law
If producers contain 5000 kJ of available energy, how much energy is approximately available to the primary consumers?
आसान भाषा में: Primary consumers को producer energy का लगभग 10% मिलता है।
✅ Solution
E₂ = 10% × 5000
E₂ = 500 kJ
Answer: 500 kJ
Numerical 2 – Secondary Consumer
EASY
Trophic Level
If primary consumers receive 800 kJ, approximately how much energy reaches secondary consumers?
Primary consumers से secondary consumers को लगभग 10% energy transfer होती है।
✅ Solution
E = 0.1 × 800
Answer: 80 kJ
Numerical 3 – Third Transfer
EASY
Energy Flow
A trophic level has 300 kJ of available energy. How much energy is expected to be transferred to the next trophic level?
बस 300 का 10% निकालना है।
✅ Solution
10% of 300 = 30 kJ
Answer: 30 kJ
Numerical 4 – Reverse Energy
EASY
Reverse 10% Law
If primary consumers have only 200 kJ of energy, estimate the energy available at the producer level.
Primary consumer energy producer energy का 10% है। इसलिए 200 को 0.1 से divide करें।
✅ Solution
Producer energy = 200 / 0.1
Answer: 2000 kJ
Numerical 5 – Three Trophic Transfers
MODERATE
Energy Pyramid
Producers contain 10,000 kJ of available energy. Estimate the energy at the fourth trophic level using the 10% transfer approximation.
Producer → first consumer → second consumer → third consumer. तीन बार 10% लेना है।
✅ Solution
First = 10,000 × 0.1 = 1000 kJ
Second = 1000 × 0.1 = 100 kJ
Third = 100 × 0.1 = 10 kJ
Answer: 10 kJ
Numerical 6 – Producer Energy
MODERATE
Reverse Calculation
A primary consumer receives approximately 600 kJ. Estimate the producer-level energy.
600 kJ producer energy का 10% है। Producer energy = 600 ÷ 0.1.
✅ Solution
Eproducer = 600 / 0.1
Answer: 6000 kJ
Numerical 7 – Secondary Level
MODERATE
Trophic Levels
If producers contain 20,000 kJ, estimate the energy available to secondary consumers.
Two transfers होंगे: 20,000 → 2,000 → 200 kJ.
✅ Solution
Primary = 20,000 × 0.1 = 2,000 kJ
Secondary = 2,000 × 0.1 = 200 kJ
Answer: 200 kJ
Numerical 8 – Higher Consumer
MODERATE
Energy Flow
Producers have 50,000 kJ of available energy. Estimate the energy at the third trophic level.
Producer → primary → secondary. दो बार 10% लेना होगा।
✅ Solution
Primary = 50,000 × 0.1 = 5,000 kJ
Secondary = 5,000 × 0.1 = 500 kJ
Answer: 500 kJ
Numerical 9 – Fourth Trophic Level
HARD
10% Law
A food chain starts with producers containing 40,000 kJ. How much energy is expected at the fourth trophic level?
Fourth trophic level तक three transfers होंगे. 40,000 → 4,000 → 400 → 40.
✅ Solution
E = 40,000 × (0.1)³
E = 40 kJ
Answer: 40 kJ
Numerical 10 – Energy at Fifth Level
HARD
Energy Pyramid
A producer level contains 100,000 kJ of energy. Estimate the energy available at the fifth trophic level using the 10% law.
Producer से fifth level तक four energy transfers होंगे।
✅ Solution
E = 100,000 × (0.1)⁴
E = 10 kJ
Answer: 10 kJ
Numerical 11 – Reverse Two Levels
HARD
Reverse Energy
A secondary consumer has approximately 50 kJ of energy. Estimate the energy present at the producer level.
Secondary level तक energy दो बार 10% हुई है। इसलिए 50 को 0.1 से दो बार divide करेंगे।
✅ Solution
Primary = 50 / 0.1 = 500 kJ
Producer = 500 / 0.1 = 5000 kJ
Answer: 5000 kJ
Numerical 12 – Energy Comparison
HARD
Comparison
If producers contain 60,000 kJ and secondary consumers receive only 600 kJ, what percentage of producer energy reaches the secondary consumers?
Secondary energy ÷ producer energy × 100 करें।
✅ Solution
Percentage = 600 / 60,000 × 100
Answer: 1%
Numerical 13 – Fourth Level from Primary
VERY HARD
Trophic Transfer
A primary consumer has 900 kJ of energy. Estimate the energy available to a fourth-level consumer if each transfer is approximately 10%.
Primary से fourth level तक तीन transfers होंगे: 900 → 90 → 9 → 0.9.
✅ Solution
E = 900 × (0.1)³
Answer: 0.9 kJ
Numerical 14 – Producer Energy from Higher Level
VERY HARD
Reverse Calculation
A fourth trophic level contains approximately 8 kJ. Estimate the producer energy using the 10% transfer approximation.
Fourth level तक तीन transfers हैं। इसलिए 8 को 0.1 से तीन बार divide करना है।
✅ Solution
Third = 8 / 0.1 = 80 kJ
Second = 80 / 0.1 = 800 kJ
Producer = 800 / 0.1 = 8000 kJ
Answer: 8000 kJ
Numerical 15 – Energy Lost
VERY HARD
Energy Loss
A producer level has 25,000 kJ. Approximately 2,500 kJ reaches the primary consumers. How much energy is not transferred to the next trophic level?
Producer energy में से transferred energy subtract करें।
✅ Solution
Energy not transferred = 25,000 - 2,500
Answer: 22,500 kJ
Numerical 16 – Multiple Transfers
VERY HARD
Energy Flow
A producer ecosystem contains 72,000 kJ. Estimate the energy at the fifth trophic level using the 10% law.
Fifth trophic level तक four transfers होंगे।
✅ Solution
E = 72,000 × (0.1)⁴
E = 7.2 kJ
Answer: 7.2 kJ
Numerical 17 – Energy Ratio
EXPERT
Energy Ratio
What is the approximate ratio of energy available at the producer level to that at the third trophic level using the 10% law?
Producer → primary → secondary means two transfers. हर transfer पर 10%, इसलिए final energy 1% होगी।
✅ Solution
Third level = 0.1 × 0.1 = 0.01 of producer level
Ratio = 1 : 0.01
Answer: Producer : Third Level = 100 : 1
Numerical 18 – Secondary to Fourth
EXPERT
Multi-Level Calculation
A secondary consumer has 450 kJ of energy. Estimate the energy available to a fifth trophic level, assuming each transfer is 10%.
Secondary → tertiary → fourth → fifth. तीन transfers हैं।
✅ Solution
E = 450 × (0.1)³
Answer: 0.45 kJ
Numerical 19 – Percentage at Higher Level
EXPERT
10% Law
If producers contain 80,000 kJ and a fourth trophic level receives approximately 80 kJ, what percentage of producer energy reaches that level?
80 को 80,000 से divide करके 100 से multiply करें।
✅ Solution
Percentage = 80/80,000 × 100
Answer: 0.1%
Numerical 20 – Final Challenge
EXPERT
Mixed Energy Flow
A producer ecosystem contains 120,000 kJ. Calculate the approximate energy available at: (a) primary consumers, (b) secondary consumers, (c) tertiary consumers, and (d) the percentage of original energy available at the tertiary level.
हर trophic transfer पर 10% energy रखें। 120000 → 12000 → 1200 → 120. फिर tertiary energy को original energy से compare करें।
✅ Step-by-Step Solution
(a) Primary = 120,000 × 0.1 = 12,000 kJ
(b) Secondary = 12,000 × 0.1 = 1,200 kJ
(c) Tertiary = 1,200 × 0.1 = 120 kJ
(d) Percentage = 120 / 120,000 × 100
Percentage = 0.1%
Answer: Primary = 12,000 kJ; Secondary = 1,200 kJ; Tertiary = 120 kJ; Original energy reaching tertiary level = 0.1%
🔎 इस difficulty में कोई numerical उपलब्ध नहीं है।

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