A circular metal plate expands under heating so that its radius increases by 2%. Find  the approximate increase in the area of the plate if the radius of the plate before heating is 10cm.

Explanation

`x=`radius & y= area

`y= pi x^2 `

`(/_x)/x xx 100 = 2`

`(/_ x)/10 xx 100 = 2`

`/_ x = 2/10= 0.2cm`

`dx= 0.2cm`

now,`y= pi x^2`

`dy/dx = 2x xx pi`

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