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JEE Main 2021 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 24 February 2021, Shift 1, Maths Q72

Question 72 of 90 in this shift, Maths question 12 of 30, Section A.

The population

P = P(t)

at time 't' of a certain species follows the differential equation

\frac{dP}{dt} = 0.5P - 450

. If

P(0) = 850

, then the time at which population becomes zero is :

(1) $\log_e 9$
(2) $\frac{1}{2}\log_e 18$
(3) $\log_e 18$
(4) $2\log_e 18$ Official answer

Official answer

Option 4

NTA final key.

Chapter: Differential Equations
Topic: Variable Separable Form
Idea tested: Physical Modeling Applications

Same idea in other shifts

Asked 2× in all

31 Jan 2024, Shift 2 · Q13The temperature $T(t)$ of a body at time $t=0$ is $160^\circ$ F and it decreases continuously as per the differential equation…EasySingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.