-
With one straight cut, snip a small triangle off one corner of a square. The cut crosses the two sides that meet at that corner. How many corners does the bigger piece have now?
The cut crosses each of the two sides partway along, not through another corner, and only the bigger piece's corners are counted.
Five.
-
A snail climbs 3 meters each day and slips 2 meters each night. Starting at the bottom, on which day does it first reach the top of a 10-meter wall?
The snail starts at the bottom in the morning, climbs 3 meters every day and slips 2 meters every night. Once it reaches the top, it stops and does not slip.
Day eight. It reaches the top that day, so it never slips back down.
-
Two US coins total 30 cents. One of them is not a nickel. Which coins are they?
Only real US coins count. "One of them is not a nickel" is true of the quarter; it does not mean the other coin cannot be a nickel.
A quarter and a nickel. The quarter is the one that is not a nickel.
-
A bat and a ball cost $1.10 altogether. The bat costs $1 more than the ball. What does the ball cost?
The bat and the ball are the only two things, and the prices are in whole cents.
Five cents. The bat costs $1.05.
-
A farmer must take a fox, a chicken, and grain across a river. The boat carries the farmer and one item. Without the farmer, the fox cannot stay with the chicken, or the chicken with the grain. How can everything cross?
Only the farmer can row the boat, and it holds the farmer plus at most one item. Trouble happens only on a bank the farmer has left, never during a crossing.
Take the chicken across. Go back alone. Take the fox across. Bring the chicken back. Take the grain across. Go back alone. Take the chicken across.
-
Anna, Beth, and Cara each have a different pet: cat, dog, or fish. Anna has neither cat nor dog. Beth does not have the dog. Who has each pet?
Each girl has exactly one pet, and no two girls have the same kind of pet.
Anna has the fish, Beth has the cat, and Cara has the dog.
-
Eight balls look identical, but one is heavier. Using a balance scale, how can you always find it in no more than two weighings?
Exactly one ball is heavier, and the other seven weigh the same. The balance scale only shows which side is heavier, or that the two sides are equal.
Weigh three against three. If they balance, weigh the last two against each other. If one side is heavier, take two balls from that side and weigh one against the other; if they balance, the third ball from that side is the heavy one.
-
In a three-digit number, the tens digit is two more than the ones digit. The hundreds digit is one less than the tens digit. The digits add to 12. What is the number?
453.