In going through A. Albert Klaf’s Calculus Refresher, republished by Dover, I came across a mistake in Appendix A. The answer to question 7 on page 88 is incorrect. The question is:
7. What are the most economical dimensions of a right circular cylindrical tank made of steel of uniform thickness and of fixed volume = 6,000 cu. ft.?
And the answer given in Appendix A, p377 is:
7. r = h = 12.41 ft
However, that would give:
V = 6004.3392
dA/dr = 78.0307
I believe the correct answer is:
r = 9.8475
h = 19.6949
A = 1827.8966
If you notice any other errors in this book, let me know in the comments.