# SCERT Maharashtra Question Bank solutions for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 chapter 1.4 - Applications of Derivatives [Latest edition]

## Solutions for Chapter 1.4: Applications of Derivatives

Below listed, you can find solutions for Chapter 1.4 of Maharashtra State Board SCERT Maharashtra Question Bank for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022.

Q.1Q.2Q.3Q.4Q.5Q.6
Q.1

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 Chapter 1.4 Applications of Derivatives Q.1

#### MCQ [1 Mark]

Q.1 | Q 1

The slope of the tangent to the curve y = x3 – x2 – 1 at the point whose abscissa is – 2, is ______.

• – 8

• 8

• 16

• – 16

Q.1 | Q 2

Choose the correct alternative:

Slope of the normal to the curve 2x2 + 3y2 = 5 at the point (1, 1) on it is

• -2/3

• 2/3

• 3/2

• -3/2

Q.1 | Q 3

Choose the correct alternative:

The function f(x) = x3 – 3x2 + 3x – 100, x ∈ R is

• increasing for all x ∈ R, x ≠ 1

• decreasing

• neither increasing nor decreasing

• decreasing for all x ∈ R, x ≠ 1

Q.1 | Q 4

If the marginal revenue is 28 and elasticity of demand is 3, then the price is ______.

• 24

• 32

• 36

• 42

Q.1 | Q 5

The price P for the demand D is given as P = 183 + 120D − 3D2, then the value of D for which price is increasing, is ______.

• D < 60

• D > 60

• D < 20

• D > 20

Q.1 | Q 6

If the elasticity of demand η = 1, then demand is ______.

• constant

• inelastic

• unitary elastic

• elastic

Q.1 | Q 7

If 0 < η < 1, then the demand is ______.

• constant

• inelastic

• unitary elastic

• elastic

Q.2

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 Chapter 1.4 Applications of Derivatives Q.2

#### Fill in the blanks [1 Mark]

Q.2 | Q 1

The slope of tangent at any point (a, b) is also called as ______.

Q.2 | Q 2

If the function f(x) = 7/x - 3, x ∈ R, x ≠ 0 is a decreasing function, then x ∈ ______

Q.2 | Q 3

The slope of the tangent to the curve x = 1/"t", y = "t" - 1/"t", at t = 2 is ______

Q.2 | Q 4

If the average revenue is 45 and elasticity of demand is 5, then marginal revenue is ______.

Q.2 | Q 5

The total cost function for production of articles is given as C = 100 + 600x – 3x2, then the values of x for which the total cost is decreasing is  ______

Q.3

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 Chapter 1.4 Applications of Derivatives Q.3

#### [1 Mark]

Q.3 | Q 1

State whether the following statement is True or False:

An absolute maximum must occur at a critical point or at an end point.

• True

• False

Q.3 | Q 2

State whether the following statement is True or False:

The function f(x) = 3/x + 10, x ≠ 0 is decreasing

• True

• False

Q.3 | Q 3

The function f(x) = x - 1/x, x ∈ R, x ≠ 0 is increasing

• True

• False

Q.3 | Q 4

State whether the following statement is True or False:

The equation of tangent to the curve y = x2 + 4x + 1 at (– 1, – 2) is 2x – y = 0

• True

• False

Q.3 | Q 5

State whether the following statement is True or False:

If the function f(x) = x2 + 2x – 5 is an increasing function, then x < – 1

• True

• False

Q.3 | Q 6

State whether the following statement is True or False:

If the marginal revenue is 50 and the price is ₹ 75, then elasticity of demand is 4

• True

• False

Q.4

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 Chapter 1.4 Applications of Derivatives Q.4

#### Solve the following: [3 Marks]

Q.4 | Q 1

Find the equations of tangent and normal to the curve y = 3x2 – x + 1 at the point (1, 3) on it

Q.4 | Q 2

Find the values of x such that f(x) = 2x3 – 15x2 + 36x + 1 is increasing function

Q.4 | Q 3

Find the values of x such that f(x) = 2x3 – 15x2 – 144x – 7 is decreasing function

Q.4 | Q 4

Show that the function f(x) = (x - 2)/(x + 1), x ≠ – 1 is increasing

Q.4 | Q 5

Divide the number 20 into two parts such that their product is maximum

Q.4 | Q 6. (i)

If the demand function is D = 50 – 3p – p2. Find the elasticity of demand at p = 5 comment on the result

Q.4 | Q 6. (ii)

If the demand function is D = 50 – 3p – p2. Find the elasticity of demand at p = 2 comment on the result

Q.4 | Q 7

If the demand function is D = ((p + 6)/(p − 3)), find the elasticity of demand at p = 4.

Q.4 | Q 8. (i)

The total cost of manufacturing x articles is C = 47x + 300x2 − x4.  Find x, for which average cost is increasing.

Q.4 | Q 8. (ii)

The total cost of manufacturing x articles C = 47x + 300x2 – x4 . Find x, for which average cost is decreasing

Q.5

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 Chapter 1.4 Applications of Derivatives Q.5

#### Solve the following: [4 Marks]

Q.5 | Q 1

Determine the maximum and minimum value of the following function.

f(x) = 2x3 – 21x2 + 36x – 20

Q.5 | Q 2

A rod of 108 m long is bent to form a rectangle. Find it’s dimensions when it’s area is maximum.

Q.5 | Q 3

Find MPC, MPS, APC and APS, if the expenditure Ec of a person with income I is given as Ec = (0.0003) I2 + (0.075) I When I = 1000

Q.5 | Q 4. (i)

The manufacturing company produces x items at the total cost of ₹ 180 + 4x. The demand function for this product is P = (240 – x). Find x for which revenue is increasing

Q.5 | Q 4. (ii)

The manufacturing company produces x items at the total cost of ₹ 180 + 4x. The demand function for this product is P = (240 − 𝑥). Find x for which profit is increasing

Q.5 | Q 5

If x + y = 3 show that the maximum value of x2y is 4.

Q.5 | Q 6

Find the equation of tangent to the curve x2 + y2 = 5, where the tangent is parallel to the line 2x – y + 1 = 0

Q.5 | Q 7

Find the equation of normal to the curve y = sqrt(x - 3) which is perpendicular to the line 6x + 3y – 4 = 0.

Q.5 | Q 8

Find the equation of tangent to the curve y = x2 + 4x at the point whose ordinate is – 3

Q.6

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 Chapter 1.4 Applications of Derivatives Q.6

#### Activity: [4 Marks]

Q.6 | Q 1

A metal wire of 36 cm long is bent to form a rectangle. By completing the following activity, find it’s dimensions when it’s area is maximum.

Solution: Let the dimensions of the rectangle be x cm and y cm.

∴ 2x + 2y = 36

Let f(x) be the area of rectangle in terms of x, then

f(x) = square

∴ f'(x) = square

∴ f''(x) = square

For extreme value, f'(x) = 0, we get

x = square

∴ f''(square) = – 2 < 0

∴ Area is maximum when x = square, y = square

∴ Dimensions of rectangle are square

Q.6 | Q 2

By completing the following activity, examine the function f(x) = x3 – 9x2 + 24x for maxima and minima

Solution: f(x) = x3 – 9x2 + 24x

∴ f'(x) = square

∴ f''(x) = square

For extreme values, f'(x) = 0, we get

x = square or square

∴ f''(square) = – 6 < 0

∴ f(x) is maximum at x = 2.

∴ Maximum value = square

∴ f''(square) = 6 > 0

∴ f(x) is maximum at x = 4.

∴ Minimum value = square

Q.6 | Q 3

By completing the following activity, find the values of x such that f(x) = 2x3 – 15x2 – 84x – 7 is decreasing function.

Solution: f(x) = 2x3 – 15x2 – 84x – 7

∴ f'(x) = square

∴ f'(x) = 6(square) (square)

Since f(x) is decreasing function.

∴ f'(x) < 0

Case 1: (square) > 0 and (x + 2) < 0

∴ x ∈ square

Case 2: (square) < 0 and (x + 2) > 0

∴ x ∈ square

∴ f(x) is decreasing function if and only if x ∈ square

Q.6 | Q 4. (i)

A manufacturing company produces x items at a total cost of ₹ 40 + 2x. Their price per item is given as p = 120 – x. Find the value of x for which revenue is increasing

Solution: Total cost C = 40 + 2x and Price p = 120 – x

Revenue R = square

Differentiating w.r.t. x,

∴ ("dR")/("d"x) = square

Since Revenue is increasing,

∴ ("dR")/("d"x) > 0

∴ Revenue is increasing for square

Q.6 | Q 4. (ii)

A manufacturing company produces x items at a total cost of ₹ 40 + 2x. Their price per item is given as p = 120 – x. Find the value of x for which profit is increasing

Solution: Total cost C = 40 + 2x and Price p = 120 − x

Profit π = R – C

∴ π = square

Differentiating w.r.t. x,

("d"pi)/("d"x) = square

Since Profit is increasing,

("d"pi)/("d"x) > 0

∴ Profit is increasing for square

Q.6 | Q 4. (iii)

A manufacturing company produces x items at a total cost of ₹ 40 + 2x. Their price per item is given as p = 120 – x. Find the value of x for which elasticity of demand for price ₹ 80.

Solution: Total cost C = 40 + 2x and Price p = 120 – x

p = 120 – x

∴ x = 120 – p

Differentiating w.r.t. p,

("d"x)/("dp") = square

∴ Elasticity of demand is given by η = - "P"/x*("d"x)/("dp")

∴ η = square

When p = 80, then elasticity of demand η = square

## Solutions for Chapter 1.4: Applications of Derivatives

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## SCERT Maharashtra Question Bank solutions for 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 chapter 1.4 - Applications of Derivatives

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Concepts covered in 12th Standard HSC Mathematics and Statistics (Commerce) Maharashtra State Board 2022 chapter 1.4 Applications of Derivatives are Introduction of Derivatives, Increasing and Decreasing Functions, Maxima and Minima, Application of Derivatives to Economics.

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