Originally Posted by
rachael 4 Joshua fell over and has a large wound on his shin. As his wound heals, the surface area of
the scab decreases. The surface area of the scab, A square centimetres, t days after the
wound was received, can be modelled by the equation A = 10 × 2−0.1t.
a What was the original surface area of Joshua’s wound?
b What is the surface area of the wound after 3 days?
c How many days after the wound was received has its surface area reduced by
i 50%? ii 95%?
d The equation for A can be re-expressed in the form A = b × e−kt, where b and k are
constants and e is the natural base.
ti Write down the value of b.
ii Find the value of k, correct to 4 decimal places.
oops... this is the question
could you help me with part d?