Select Page

# logic11to20 ( ** )

### Logic problems (‘brain teasers’) — Problems 11 to 20

The ten problems are presented first, followed by the solutions to the ten problems.

Problem 11:

There are 20 apples in a crate, and 20 persons in a room with the crate.  You need to distribute the apples so that everyone gets one apple (not including yourself), but so that you still have one apple left in the crate.  How can you do this?  Is it possible?

Problem 12:

What can you fill a pitcher with so that it is lighter than if it is full of air?

Problem 13:

Two men order coffee at a restaurant.  One of the men found a fly in his coffee and asked the waiter to take away the coffee with the fly and to bring him back a fresh cup of coffee.  The waiter soon returned with another cup of coffee.  The man became upset and angrily declared that the waiter had brought him back the very same cup, only with the fly removed.  How did he know?

Problem 14:

If each child in a certain family has at least three brothers and two sisters, then what is the smallest number of children that the family can have?

Problem 15:

Ruth’s mother had four children.  The first was named Spring, the second was named Summer, and the third was named Autumn.  What was the name of her fourth child?

Problem 16:

Two men are identical in appearance.  They have the same mother and the same father, and they have the same birth date.  When asked if they are twins, they honestly respond, “No, we are not.”  How is this possible?

Problem 17:

A bag contains ten \$5 bills, 10 \$10 bills, and 10 \$20 bills.  Sue is blindfolded and is told that she can draw bills out of the bag, one at a time, until she has three bills of the same denomination, then she must stop drawing bills.  What is the largest amount of money Sue can draw out of the bag?

Problem 18:

A

Problem 19:

T

Problem 20:

U

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Solution to Problem 11:

• Distribute 19 apples to 19 of the people, and then hand the crate with the remaining apple in it to the twentieth person.

Solution to Problem 12:

• Holes!

Solution to Problem 13:

• He had put sugar in the coffee before he discovered the fly, and the second cup of coffee contained sugar as he tasted it.

Solution to Problem 14:

• There must be at least seven children — four boys and three girls.

Solution to Problem 15:

• The problem stated that RUTH’s mother had four children.  The name of the fourth child must obviously be RUTH!  Did you take the bait??

Solution to Problem 16:

• The two men must be two of the children from a set of triplets, or quadruplets, etc.

Solution to Problem 17:

• The largest amount of money Sue can draw out of the bag is \$90  (two \$5 bills, two \$10 bills, and three \$20 bills).

Solution to Problem 18:

•    T

Solution to Problem 19:

• T

Solution to Problem 20:

• 8