1. The equation is correct if you turn it upside down (180 degrees).
2. I know of 2 possible answers, each a mirror of the other. There may be a few other correct answers as well, but be sure that the tunnels don't cross in any place.
A. N 30, E 15, N 12, W 7, N 11, W 10, S 8, E 2, S 13, W 7, S 27, E 5, S 5, E 2.
B. N 30, W 15, N 12, E 7, N 11, E 10, S 8, W 2, S 13, E 7, S 27, W 5, S 5, W 2.
3. If 73% of the students are psychology majors, we know that 27% are not psychology majors. By the same reasoning, 38% are not business majors, because 62% of the students do major in business. So:
27 + 38 = 65
65% of the students are not majoring in both psychology & business, so 35% are double majors, a total of 70 students.
5. A Thoroughfare.
6. The knight can land on all of the 9 squares except for the center 1, so the answer is 8.
7. Ram. Each step in the series refers to a sign of the zodiac. Every other zodiac sign is used. I'd like to thank Esa Kuusela for spotting a serious error in the original problem posted here, which was subsequently replaced by this one.
8. You are able to swim downstream at 3 miles an hour, & upstream at 2 miles an hour. There is a difference of 1 mile an hour, which is the river helping you in 1 direction, & slowing you in the other direction. Average the 2 rates, & you have the rate that you can swim in still water, which is 2.5 miles an hour. You can thus swim a mile in still water in 24 minutes.
9. Vos. A very tricky puzzle! The adjective form of cattle is bovine. Remove the ine, read it backward, & then add an s, & you have vobs. By the same reasoning, bear = ursine = srus, horse = equine = uqes, pigs = porcine = crops, & sheep = ovine = vos. Even if you got this extremely difficult puzzle right, please don't go around calling animals by these names!
10. 36. You will need 3 of numbers 0, 7, 8 & 9, & 4 of numbers 1-6.