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## Homework Statement

The volume of a spherical balloon of radius 'r' is Vcm^3, where V =4/3pir^3

The volume of the balloon increases with time 't' seconds according to the formula

dV/dt = 1000/(2t+1)^2, t>0

i) Find an expression in terms of 'r' and 't' for dr/dt

ii) Given that V = 0 and t = 0, solve the differential equation

dV/dt = 1000/(2t+1)^2, to obtain V in terms of t

iii) Find the radius of the balloon at time t =5

iv) Find the rate of increases of the radius of the balloon

## Homework Equations

## The Attempt at a Solution

i) Well we know dV/dt = (dv/dr) x (dr/dt)

Which means that I found dr/dt to be - (250/ (pir^2(2t+1)^2))

For the rest of them, i have no clue what to do. :S

Thanks in advance