Ex 6.4, 5 Find the approximate change in the surface area of a cube of side x meters caused by decreasing the side by 1%.Let side of the cube = x meters. Given Decrease in side = 1% = − 0.01 x Hence, ∆ x = −0.01 x Surface area of the cube = S = 6x2 m2 We need to find the approximate change in the surface area of the cube i.e. ∆ S Now, ∆ S = 𝑑𝑠/𝑑𝑥 ∆x = 𝑑(6𝑥^2 )/𝑑𝑥 ∆x = 12x (−0.01x) = − 0.12x2 Hence, the approximate change is 0.12x2 m2

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.

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