Question

The radius of a circular plate increases at the rate of 0.1 cm/sec. At what rate does the area increase when the radius of plate is 5/11 cm. Plz answer correctly​

Answer 1

Answer:

given, dr/dt = 0.1 cm/sec find => dA/dt = ?

we know area of circle i.e A = πr²

=> dA/dt = (2πr)dr/dt

=> dA/dt = 2πr×0.1 = 0.2πr

now at r = 5/11

=> dA/dt = 0.2π(5/11) = 0.2(22/7)(5/11)

=> dA/dt = 2/7 = 0.285 cm²/sec

Answer 2

Explanation:

Atp,

dt

dr

=+0.01

dt

dA

=

10

π

A=Πr

2

dt

dA

=2πr

dt

dr

10

π

=2πr∗0.01

r=

0.2

1

=5cm