RD Sharma

A tank with rectangular base and rectangular sides, open at the top is to be constructed so that its depth is 2 m and volume is 8 m3. If building of tank cost Rs 70 per square metre for the base and Rs 45 per square metre for sides, what is the cost of least expensive tank?

Let the length, breath and height of tank be $I, b$ and $h$ respectively. Also, assume volume of tank as $V$ \[h\text{ }=\text{ }2\text{ }m\text{ }\left( given \right)\] \[V\text{ }=\text{ }8\text{...

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A rectangular sheet of tin 45 cm by 24 cm is to be made into a box without top, by cutting off squares from each corners and folding up the flaps. What should be the side of the square to be cut off so that the volume of the box is maximum possible?

Given length of rectangle sheet \[=\text{ }45\text{ }cm\] Breath of rectangle sheet \[=\text{ }24\text{ }cm\] Let the side length of each small square be $a.$ If by cutting a square from each corner...

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A square piece of tin of side 18 cm is to be made into a box without top by cutting a square from each corner and folding up the flaps to form a box. What should be the side of the square to be cut off so that the volume of the box is maximum? Also, find this maximum volume

Given side length of big square is $18 cm$ Let the side length of each small square be $a.$ If by cutting a square from each corner and folding up the flaps we will get a cuboidal box with Length,...

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A wire of length 20 m is to be cut into two pieces. One of the pieces will be bent into shape of a square and the other into shape of an equilateral triangle. Where the wire should be cut so that the sum of the areas of the square and triangle is minimum?

Suppose the wire, which is to be made into a square and a triangle, is cut into two pieces of length $x$ and $y$ respectively. Then, \[x\text{ }+\text{ }y\text{ }=\text{ }20\text{ }\Rightarrow...

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A wire of length 28 m is to be cut into two pieces. One of the pieces is to be made into a square and the other into a circle. What should be the lengths of the two pieces so that the combined area of the circle and the square is minimum?

Suppose the given wire, which is to be made into a square and a circle, is cut into two pieces of length $x$ and $y$ $m$ respectively. Then, \[x\text{ }+\text{ }y\text{ }=\text{ }28\text{...

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Let A = {1, 2, 3}, and let R1 = {(1, 1), (1, 3), (3, 1), (2, 2), (2, 1), (3, 3)}, R2 = {(2, 2), (3, 1), (1, 3)}, R3 = {(1, 3), (3, 3)}. Find whether or not each of the relations R1, R2, R3 on A is
(i) reflexive
(ii) symmetric
(iii) transitive.

Solution: Consider R1 Given R1 = {(1, 1), (1, 3), (3, 1), (2, 2), (2, 1), (3, 3)} Reflexivity: Here, (1, 1), (2, 2), (3, 3) ∈R So, R1 is reflexive. Symmetry: Here, (2, 1) ∈ R1, But (1, 2) ∉ R1...

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Test whether the following relation R1, R2, and R3 are
(i) reflexive
(ii) symmetric and
(iii) transitive:
(i) R1 on Q0 defined by (a, b) ∈ R1 ⇔ a = 1/b.
(ii) R2 on Z defined by (a, b) ∈ R2 ⇔ |a – b| ≤ 5
(iii) R3 on R defined by (a, b) ∈ R3 ⇔ a2 – 4ab + 3b2 = 0.

Solution: (i) Given R1 on Q0 defined by (a, b) ∈ R1 ⇔ a = 1/b. Reflexivity: Let a be an arbitrary element of R1. Then, a ∈ R1 ⇒ a ≠1/a for all a ∈ Q0 So, R1 is not reflexive. Symmetry: Let...

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Three relations R1, R2 and R3 are defined on a set A = {a, b, c} as follows: R1 = {(a, a), (a, b), (a, c), (b, b), (b, c), (c, a), (c, b), (c, c)}
R2 = {(a, a)}
R3 = {(b, c)}
R4 = {(a, b), (b, c), (c, a)}. Find whether or not each of the relations R1, R2, R3, R4 on A is
(i) reflexive
(ii) symmetric and
(iii) transitive.

Solution: (i) Consider R1 Given R1 = {(a, a), (a, b), (a, c), (b, b), (b, c), (c, a), (c, b), (c, c)} Now we have check R1 is reflexive, symmetric and transitive Reflexive: Given (a, a), (b, b) and...

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Let A be the set of all human beings in a town at a particular time. Determine whether of the following relation is reflexive, symmetric and transitive:
(i) R = {(x, y): x and y work at the same place}
(ii) R = {(x, y): x and y live in the same locality}

Solution: (i) Given R = {(x, y): x and y work at the same place} Now we have to check whether the relation is reflexive: Let x be an arbitrary element of R. Then, x ∈R ⇒...

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Find the points of local maxima or local minima and corresponding local maximum and local minimum values of each of the following functions. Also, find the points of inflection, if any: (i) f(x) = (x – 1) (x + 2)^2 (ii) f (x) = 2/x – 2/x^2, x > 0

(i) Given $f(x)=(x-1)(x+2)^{2}$ $ \begin{array}{l} \therefore \mathrm{f}(\mathrm{x})=(\mathrm{x}+2)^{2}+2(\mathrm{x}-1)(\mathrm{x}+2) \\ =(\mathrm{x}+2)(\mathrm{x}+2+2 \mathrm{x}-2) \\...

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Find the points of local maxima or local minima and corresponding local maximum and local minimum values of each of the following functions. Also, find the points of inflection, if any: (i) f(x) = x^4 – 62x^2 + 120x + 9 (ii) f (x) = x^3 – 6x^2 + 9x + 15

(i) Given $f(x)=x^{4}-62 x^{2+} 120 x+9$ $ \begin{array}{l} \therefore \mathrm{f}(\mathrm{x})=4 \mathrm{x}^{\mathrm{a}}-124 x+120=4\left(\mathrm{x}^{a}-31 \mathrm{x}+30\right) \\...

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