A. 2¾ miles
b. 22 laps/hr
c. 12 laps

Differentiate both sides, treating
as a function of
. Let's take it one term at a time.
Power, product and chain rules:



Product and chain rules:




Product and chain rules:




The derivative of 0 is, of course, 0. So we have, upon differentiating everything,

Isolate the derivative, and solve for it:


(See comment below; all the 6s should be 2s)
We can simplify this a bit by multiplying the numerator and denominator by
to get rid of that fraction in the denominator.

Hope this isn't too confusing
All of the numbers have different shortcuts.
1. Yes. Divisible by 4: if last two digits are divisible by 4 then the whole number is yes)
2. No. Divisible by 6: it must be even and when you add them up, (44) it must be divisible by 3 (no, 44 is not divisible by 3)
3. Divisible by 8: ( last 3 numbers are divisible by 8 (312) = 39 ( yes it is)
4 Yes. Divisible by 11: ( sum of digits at odd places and sum of digits at even spaces,is either 0 or divisible by 11) yes, 278949. (2+8+9) + (7+9+9)= 19 + 25 = 44 and 44 is divisible by 11)
5. No. Divisible by 12 (divisible by 3 and 4, sum of digits is divisible by 3 ; and last 2 digits divisible by 4: 87654395 : 52/3= 18 (yes) 95/4(no) this number not divisible by 12
6. No. Divisible by 15: divisible by 3 and 5 ..87654385 = 46/3 = 15..(No) divisible by 5 yes. The number is not divisible by 15