We have found in part (i) that

.

Now part (ii) asks us when is the temperature equal to 100.

So we are solving

.

Now you have

and using the definition of logarithms we have

so

s… it cooled fairly quickly there in fairness!

Alternatively note that and are inverse functions so if we apply to both sides of we have

and continue on.

Regards,

J.P.

Is there any chance you have a solution to Q 3 (c) on the sample paper we have? I’m ending up with but I think I’ve gone wrong somewhere.

Thanks.

]]>