Controversial problems 'you solve'

Let's go find solutions to interesting problems that made many people "scratch their hair".

Problem 1: Problem 50,000

You want to buy a 97,000 dress but don't have money. You borrow 50,000 and you borrow 50,000, your total is 100,000. You buy the dress and get 3,000 extra money.

You return the 1,000 father, mother 1,000 and keep 1,000. Now you owe your mother 49,000 vs father 49,000. Total: 49,000 + 49,000 = 98,000 + 1,000 = 99,000. Ask: Where did the remaining 1,000 go?

Problem 2: 4 men cross the bridge

Illustration.

There are 4 men who need to go through a very dangerous bridge in the dark. Unfortunately there is only one torch, no torch cannot cross the bridge.

The bridge is very weak so each turn is only 2 people. However, the time of 4 people (A, B, C, D) crossing the bridge is not the same, respectively A - 1 minute, B - 2 minutes, C - 7 minutes, D - 10 minutes. How long is the shortest time for 4 men to cross the bridge?

Problem 3: Pay salaries for servants

Illustration.

A servant who works for the boss for 7 days is complete. The servant asked to be paid 1/7 of the gold bar every day. The boss has to cut at least how many lines and cut how to pay him exactly 1/7 of the gold ingot every day?

Problem 4: Ball in the box

Illustration.

Four balls are placed in a box. One fruit is green, one is black and the other is yellow. Shake the box and remove 2 balls. Know that there is at least one yellow fruit. Ask how many chances for the 2nd ball to be yellow?

The answer

That problem of 1: 1,000 does not disappear

After buying a skirt, you definitely have 3,000 leftovers. You return 1,000, pay your mother 1,000, so you only owe each person: 50,000 - 1,000 = 49,000, total debt owed to parents: 49,000 + 49,000 = 98,000. And you have 1,000 leftovers.

Come here,

- If you give 1,000 notes to a parent, you only owe your parents: 98,000 - 1,000 = 97,000 - equal to the value of the dress you bought.

- If you retain 1,000 and 97,000 values, the dress will have a total of 98,000, equal to the amount owed to parents

Therefore, you will not lose any money.

Problem 2: 17 minutes

The first plan most people think of is to get the fastest man ahead and the first one will turn around to guide the other three over the bridge one after another.

A total of 10 minutes (D) + 1 minute (A return) + 7 minutes (A + C) + 1 minute (A return) + 2 (A + B) = 21 minutes. If so, the problem is too easy.

To reduce time, we should find ways for D and C to go together. If they go over the first bridge, they will need a person to come back to pick up another person.

That is too time consuming. Try to let A go with B and let A wait on the other side of the bridge. After B comes back, C and D will cross the bridge and give torch to A to welcome B to.

A and B over the bridge => 2 minutes

B returned => 2 minutes

C and D over the bridge => 10 minutes

A return => 1 minute

A and B over the bridge => 2 minutes

Total is: 2 + 2 + 10 + 1 + 2 = 17 minutes

Problem 3:

The bar on the gold bar 6 bars divided into 7 equal parts. Use 2 slices to cut into 3 parts 1/7, 2/7 and 4/7 gold bars.

Day 1: Give people to 1/7 bars

Day 2: Give the servant 2/7 bars and take back 1/7 ingots

Day 3: Give people to 1/7 bars

Day 4: Give the servant 4/7 bars, get back 2 parts 1/7 and 2/7 bars

Day 5: Give people to 1/7 bars

Day 6: Give the servant 2/7 bars and take back 1/7 ingots

Day 7: Bringing the remaining 1/7 bar.

Problem 4: ratio 1/5

6 pairs of balls may have been taken out:

Gold + Gold / Gold + Blue / Green + Gold / Gold + Black / Black + Gold / Green + Black.

Since there is at least one yellow ball, make sure the Blue + Black pair cannot be removed.

So there are 5 possibilities left. So the chance for the Gold + Gold pair is 1/5.

It is possible that many people cannot accept this answer but must be 1/3. A third sentence is only true if the balls are drawn in turn and the first ball is yellow.

However, in case two balls are drawn at the same time and the color of the first ball in the two balls is given, then the 1/5 answer above is correct.

1. Try answering 5 "brain damage" interview questions below to see if you qualify for Google!
2. Quiz you solve the problem "brain damage" to the computer must also "bundle" this