Mathematics Part-II

Book: Mathematics Part-II

Chapter: 9. Differential Equations

Subject: Maths - Class 12th

Q. No. 20 of Exercise 9.4

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20

In a bank, principal increases continuously at the rate of r% per year. Find the value of r if Rs 100 double itself in 10 years (loge2 = 0.6931).

let t be time

p be principal


r be rate of interest


according the information principal increases at the rate of r% per year.



Separating variables,



Integrating both sides,





Given that t = 0, p = 100.



Now, if t = 10, then p = 2×100 = 200


So,








So r is 6.93%.


20

Chapter Exercises

Exercise 9.1
Exercise 9.2
Exercise 9.3
Exercise 9.4
Exercise 9.5
Exercise 9.6
Miscellaneous Exercise

More Exercise Questions

1

For each of the differential equations in question, find the general solution:
2

For each of the differential equations in question, find the general solution:
3

For each of the differential equations in question, find the general solution:
4

For each of the differential equations in question, find the general solution:

sec2x tan y dx + sec2y tan x dy
5

For each of the differential equations in question, find the general solution:

(ex + e–x)dy – (ex – e–x)dx = 0
6

For each of the differential equations in question, find the general solution:
7

For each of the differential equations in question, find the general solution:

y log y dx – x dy = 0
8

For each of the differential equations in question, find the general solution:
9

For each of the differential equations in question, find the general solution:
10

For each of the differential equations in question, find the general solution:

extan y dx + 1(1 – ex)sec2y dy = 0
11

For each of the differential equations in question, find a particular solution satisfying the given condition:

(x3 + x2 + x + 1) dy/dx = 2x2 + x, y = 1 when x = 0
12

For each of the differential equations in question, find a particular solution satisfying the given condition:

x(x2 – 1) dy/dx = 1; y = 0 when x = 0
13

For each of the differential equations in question, find a particular solution satisfying the given condition:

cos dy/dx = a; y = 2 when x = 0
14

For each of the differential equations in question, find a particular solution satisfying the given condition:

dy/dx = y tan x; y = 1 when x = 0
15

Find the equation of a curve passing through the point (0, 0) and whose differential equation is y′ = ex sin x
16

For the differential equation find the solution curve passing through the point (1, –1).
17

Find the equation of a curve passing through the point (0, –2) given that at any point (x, y) on the curve, the product of the slope of its tangent and y coordinate of the point is equal to the x coordinate of the point.
18

At any point (x, y) of a curve, the slope of the tangent is twice the slope of the line segment joining the point of contact to the point (– 4, –3). Find the equation of the curve given that it passes through (–2, 1).
19

The volume of spherical balloon being inflated changes at a constant rate. If initially its radius is 3 units and after 3 seconds it is 6 units. Find the radius of balloon after t seconds.
20

In a bank, principal increases continuously at the rate of r% per year. Find the value of r if Rs 100 double itself in 10 years (loge2 = 0.6931).
21

In a bank, principal increases continuously at the rate of 5% per year. An amount of Rs 1000 is deposited with this bank, how much will it worth after 10 years (e0.5 = 1.648).
22

In a culture, the bacteria count is 1,00,000. The number is increased by 10% in 2 hours. In how many hours will the count reach 2,00,000, if the rate of growth of bacteria is proportional to the number present?
23

The general solution of the differential equation is