The radius of a circular disc is increasing at a constant rate of 0.003cm/s. Find the rate at which the area is increasing when the radius is 20cm.

The rate at which the area is increasing, dA/dt, can be written with terms we know or can find out easily: dA/dt=dA/dr x dr/dt.Area of a disc, A = (pi)r^2dA/dr=2(pi)rRate of change of radius, dr/dt=0.003cm/sTherefore, dA/dt=2(pi)r x 0.003= 2(pi) x 20 x 0.003=0.12(pi)= 0.377cm^2/s

HH
Answered by Henry H. Maths tutor

11419 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Find the equation of the the tangent to the curve y=x^3 - 7x + 3 at the point (1,2)


Find CO-Ordinates of intersection of 2x+3y=12 and y=7-3x


Differentiate 2x^3 - xy^2 - 4


Solve the following equation for k, giving your answers to 4 decimal places where necessary: 3tan(k)-1=sec^2(k)


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences