Here are the key steps: 1. Wait for the guard to leave their post, which takes 8 minutes 2. Start walking across the bridge towards the other side 3. After 7 minutes, you will have passed the guard's post 4. Turn around and walk back the way you came 5. If you meet the guard returning, they will send you to the other side This allows crossing the bridge without the guard stopping you.

1. Puzzles
Boyu Li

2. There is a very slippery wall that is 11
feet high. A snail began to climb the
wall. It can climb about 5 feet in one
hour, but the snail need one hour rest
after climbed an hour. During the hour
for rest, it slipped down about 3 feet.
So how many hours Snails need to
climb to the top of the wall?

3.  The following is eight letters , find out what the last
letter is?
O,T,T,F,F,S,S,E,？

4.  One day, A man came to John’s shop, and he
bought a T-shirt. The T-shirt cost 15 euro, and the
retail price is 21 euro. The man give john 50 euro,
but john doesn‘t have change, So he went to next
door for change.
 After the man leave, john’s neighbor find out the 50
euro is counterfeit. So john pay another 50 euro to
he’s neighbor.
 Q: How much is john loss??

5.  There has 6 cups in a row, 3 with water and 3 is
empty. Can you just do one move to make:
 There do not have two empty cup together.
 And do not have two cup with water together.

6.  If there has 4 houses A,B,C,D in a Row and
 A and B is neighbor
 A and D is not neighbor
 D and C is not neighbor
Q: who is C’s neighbor

7. 1 1 2 2 3 ? 3
2 5 1 4 0 3 9

8.  Here has 12 balls, one of them has different weight
then others. If give you a balance, Can you find out
the different ball and use balance three times.

9. 1 1 1 1
1 1 1 A B
1 1 1 1
1 1 1 1 1 1
1 1
1 1
1
1 1
1 1 1 1 1
1 1 1 1
1 1
1 1
1 1 1 ?
1 1
C D
1 1

10.  The boarder of A and B country is a bridge, there
have a guard stand in middle of bridge to stop
people go through the bridge. If people come from
A, the guard will stop him and send him back to A.
If people come from B, the guard will send him back
to B.
 To cross the bridge at least need 10 minutes.
 The guard only can leave the outpost in 8 minutes.
Q: How to cross the bridge.

11. There is a very slippery wall that is 11
feet high. A snail began to climb the
wall from the bottom. It can climb
about 5 feet in one hour, but the snail
need one hour rest after climbed an
hour. During the hour for rest, it
slipped down about 3 feet. So how
many hours Snails need to climb to the
top of the wall?
1. 5-3=2
2. 11 – 5 = 6
3. 6 / 2 = 3 hours
4. 3 +1 = 4 hours

12.  The following is eight letters , find out what the last
letter is?
O ne
T wo
T hree
F our
F ive
S ix
S even
E ight
N ine

13.  One day, A man came to John’s shop, and he
bought a T-shirt. The T-shirt cost 15 euro, and the
retail price is 21 euro. The man give john 50 euro,
but john doesn‘t have change, He went to next door
for change.
 After the man leave, john’s neighbor find out the 50
euro is counterfeit. So john pay another 50 euro to
he’s neighbor.
 Q: How much is john loss??
 Ans: 44 The man get a T-shirt and 29 euro change.
That is 15 + 29 = 44

14.  There has 6 cups in a row, 3 with water and 3 is
empty. Can you just do one move to make:
 There do not have two empty cup together.
 And do not have two cup with water together.

15.  If there has 4 houses A,B,C,D in a Row and
 A and B is neighbor
 A and D is not neighbor
 D and C is not neighbor
Q: who is C’s neighbor AB C D
AB D C
C AB D *
D C AB

16. 1 1 2 2 3 ? 3
2 5 1 4 0 3 9
12 + 2 + 1 = 15
15 + 1 + 5 = 21
21 + 2 + 1 = 24
24 + 2 + 4 = 30
30 + 3 + 0 = 33
33 + 3 + 3 = 39

17.  Here has 12 balls, one of them has different weight
then others. If give you a balance, Can you find out
the different ball and use balance three times.
• Divide 12 balls into 3 groups
• Pick any two groups and
weighing them:
• If there are same, pick any
two balls in the third group
and weighing them:
• If the weight is same,
another one is different.
• If the weight is different,
pick one from them and
weighing with ball from
other group.

18. A B
1 1 1 1
1
1 1 1
1 1
1 1 1
1 1
1 1 1 1
1
1 1
1
1 1
1 1
1 1 1 1
1 1
1 1
1 1
1 1 1 ? C D
The same cell appeared in first table
1 1
and second table, will not appeared
1 1 in the third table.

19.  The boarder of A and B country is a bridge, there have a guard
stand in middle of bridge to stop people go through the
bridge. If people come from A, the guard will stop him and
send him back to A. If people come from B, the guard will
send him back to B.
 To cross the bridge at least need 10 minutes.
 The guard only can leave the outpost in 8 minutes.
Q: How to cross the bridge.
Answer: if from A to B, when the guard leave the outpost, start
walk to B, after 7 minutes, you have already pass the outpost,
and then turn round, forward to A. If you meet the guard when
he back, he will send you to B.