Thinking Logically

# Thinking Logically

## Thinking Logically

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1. Thinking Logically August 20, 2013

2. Busses for a Field Trip How many busses do you need for a field trip if each bus can hold up to 70 people and 175 people are attending the field trip?

3. Solution • The answer is 3 busses. They might not be full, but they still need 3. • Sadly, many otherwise intelligent people will answer 2.5 busses.

4. Parking Spaces

5. Crossing the River • You have a boat and need to take a fox, a chicken, and some corn across a river. • The boat will only hold you and one other thing. • If you leave the chicken alone with the corn, the chicken will eat the corn. • If you leave the fox alone with the chicken, the chicken's in big trouble. • How can you get them all across in the least amount of trips possible?

6. Solution The chicken is the problem and must never be left alone with the fox or the food. • Row chicken across and drop off on other side • Row back • Pick fox or food (doesn’t matter) and row to other side and drop off • Pick up chicken and take back to first side and drop off. • Pick up fox or food (which ever is there) and row to other side and drop off • Row back • Pick up chicken and row to other side

7. Cat in the Well • A cat is at the bottom of a 20 foot well.  (Don't worry, he's got lots of food, water, catnip and cat toys down there.) • Each day, he climbs up 5 feet... • And each night, he slides down 4 feet. • How many days will it take him to reach the top of the well?

8. Solution • Even though he gains a foot a day, it will not take him 20 days to get out of the well. • On day 15, he will be at the top of the well and will not slide down four feet because he will be out.

9. Two Doors • You are trapped in a room with two doors...  One door lead to certain freedom and the other leads to death.  You don't know which door is the good door. • There are two guards in the room.  One guard always tells the truth and the other guard always lies.  You don't know which one is honest and which one is the liar. • If you just guessed, you'd have a 50-50 shot. • To figure out which door to choose, you get to ask one guard one question. • What is your question and which guard will you ask?

10. Solution: What door will the other guard say is safe? • Both are pointing to the wrong door, so you take the one they are not pointing to. • If you ask the Liar guard, he knows the truthful guard will say the correct door so he lies and says the wrong door. • If you ask the Truthful guard, he knows the liar will tell you the wrong door, so he points to the wrong door.

11. Extra Curricular Activities Merry, Pippin, and Kate all have after school activities. Your job is to find out who does what activity and when they do it. People: Merry, Pippin, and KateAfter school activities: swimming, running, and gymnasticsDays: Wednesday, Thursday, and Friday Clues:1) After school on Thursday, the swimmer goes to lessons.2) Kate's activity happens every Friday.3) Pippin is training to be a runner.

12. Solution • After school on Thursday, the swimmer goes to lessons. This means that swimming doesn’t happen on Friday or Wednesday. 2) Kate's activity happens every Friday. So Kate is not the swimmer since that happens on Thursday. Also means that Pippin and Merry can’t have activities on Friday. 3) Pippin is training to be a runner. Since he runs, he is not the swimmer or the gymnast. This means he has to do his activity on Wednesday. Kate is the gymnast and practices on Friday. Merry is the swimmer and practices Thursday.