A biologist studied the population of rats in a barn. He found that the average natality was \(250\), average mortality \(240\), immigration \(20\) and emigration \(30\). The net increase in population is

A \(5\)
B zero
C \(10\)
D \(15\)

Verified Solution

Answer & Solution

Correct Answer

(B) zero

Step-by-step Solution

Detailed explanation

(b) : Natality and immigration positively contribute to the population growth while mortality and emigration are negative factors. In the given question,The net increase in population is natality + immigration = \(250 + 20 = 270 \) The net decrease in population is mortality + emigration = \(240 + 30 = 270\) Thus, net increase in population = \(270 -270 = 0\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

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NEET 2019 Medium

Match List \(I\) with List \(II\).

List \(I\)	List \(II\)
\(A\). Heroin	\(I\). Effect on cardiovascular system
\(B\). Marijuana	\(II\). Slow down body function
\(C\). Cocaine	\(III\). Painkiller
\(D\). Morphine	\(IV\). Interfere with transport of dopamine

Choose the correct answer from the options given below:

NEET 2023 Medium

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