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# Solution for Find the Percentage Error in Calculating the Surface Area of a Cubical Box If an Error of 1% is Made in Measuring the Lengths of Edges of the Cube ? - CBSE (Science) Class 12 - Mathematics

#### Question

Find the percentage error in calculating the surface area of a cubical box if an error of 1% is made in measuring the lengths of edges of the cube ?

#### Solution

Let x be the edge of the cube and y be the surface area.

$y = x^2$

$\text { Let } ∆ x \text { be the error in x and } ∆ y \text { be the corresponding error in } y .$

$\text { We have }$

$\frac{∆ x}{x} \times 100 = 1$

$\Rightarrow 2x = \frac{x}{100} \left[ \text { Let } dx = ∆ x \right]$

$\text { Now }, y = x^2$

$\Rightarrow \frac{dy}{dx} = 2x$

$\therefore ∆ y = \frac{dy}{dx} \times ∆ x = 2x \times \frac{x}{100}$

$\Rightarrow ∆ y = 2\frac{x^2}{100}$

$\Rightarrow ∆ y = 2\frac{y}{100}$

$\Rightarrow \frac{∆ y}{y} = \frac{2}{100}$

$\Rightarrow \frac{∆ y}{y} \times 100 = 2$

Hence, the percentage error in calculating the surface area is 2.

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Solution Find the Percentage Error in Calculating the Surface Area of a Cubical Box If an Error of 1% is Made in Measuring the Lengths of Edges of the Cube ? Concept: Approximations.
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