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Find the value of $k$ and the rate at which the mass is rising on this day.
Mathematics 9709 · AS & A Level · Differentiation
Differentiation — practice question
A watermelon is taken to have a spherical shape while it grows. Its mass, $M$ kg, and radius, $r$ cm, are linked by $M = kr^3$, where $k$ is constant. The radius is also assumed to increase at a steady rate of $0.1$ centimetres per day. On one particular day, the radius is $10$ cm and the mass is $3.2$ kg.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “From $1000k = 3.2$, obtain $k = \frac{3.2}{1000} = \frac{2}{625}$” …
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