Thread: 5th Grade Math Puzzles.

Puzzle 1

My number is less than 30.
My number of tiles will make a square.
My number of tiles will make a rectangle 2 tiles wide.
My number is greater than 5.

Answer: 16

Puzzle 2

My number of tiles will make a rectangle 3 tiles wide.
My number of tiles will make a rectangle 4 tiles wide.
My number is greater than 20.
My number is less than 30.

Answer: 24

Puzzle 3

My number of tiles will make a rectangle 4 tiles wide.
My number of tiles will make a rectangle 2 tiles wide.
My number of tiles will make a rectangle 5 tiles wide.
My number is less than 50.

Answer: 40

Puzzle 4

My number is less than 25.
My number of tiles will make only one rectangle.
My number is odd.
My number is a factor of 36.

Answer: 9 if you count a square as a rectangle, 3 if you count three tiles in a row as a rectangle.

Puzzle 5

You say my number when you start at 0 and count by 15’s.
You say my number when you start at 0 and count by 25’s.
My number is less than 200.
My number is even.

Answer: 150


Puzzle 6

My number has three digits.
My number is less than 300.
My number is a multiple of 40.
My number is a multiple of 60.

Answer: 120

Puzzle 7

My number is a square number.
My number has two digits.
My number is a multiple of 9.
My number is even.

Answer: 36

Puzzle 8

My number is prime.
My number is a factor of 42.
My number is less than 10.
My number is a factor of 70.

Answer: 7

Puzzle 9

My number is a factor of 60.
My number has two digits.
The sum of the digits in my number is 3.
One factor of my number is 4.

Answer: 12

Puzzle 10

My number is not a factor of 20.
My number is a factor of 42.
My number is less than 30.
My number is even.

Answer: 6

Puzzle 11

My number is a square number.
My number is even.
My number is less than 100.
My number is prime.

Answer: impossible. A prime number's only factors are itself and 1. If it is a square, it is either 1 (not even) or the product of a lesser number times itself (not prime). The only even prime number is 2.

Puzzle 12

My number is a multiple of 35.
My number is a multiple of 25.
My number is a multiple of 2.
My number is less than 400.

Answer: 350

Puzzle 13

My number is odd.
My number has two digits.
My number is a multiple of 3.
The sum of the digits in my number is greater than 15.

Answer: 99

My number is less than 200.
My number is a multiple of 11.
My number has three digits.
The sum of the digits in my number is 10.

Answer: 154

Your additional answers are indeed correct. Once I had one answer, I stopped looking (i.e. thinking).

Originally Posted by RYou

Puzzle 1 Answer: 16
Puzzle 2 Answer: 24
Puzzle 3 Answer: 40
Puzzle 4 Answer: 3
Puzzle 5 Answer: 75
Puzzle 6 Answer: 240
Puzzle 7 Answer: 36
Puzzle 8 Answer: 7
Puzzle 9 Answer: 12
Puzzle 10 Answer: 6
Puzzle 11 Answer: 2
Puzzle 12 Answer: 350
Puzzle 13 Answer: 99
Puzzle 14 Answer: 154

Good job RYou!. I am not sure 2 can be the correct solution to Puzzle 11 because 2 is not a square number, (is it?) The square root of 2 is an irrational number so therefore 2 is not a square (Pythagoras's constant). At least that's my thinking. What is your rationale?

Originally Posted by RYou

Puzzle 1 Answer: 16
Puzzle 2 Answer: 24
Puzzle 3 Answer: 40
Puzzle 4 Answer: 3
Puzzle 5 Answer: 75
Puzzle 6 Answer: 240
Puzzle 7 Answer: 36
Puzzle 8 Answer: 7
Puzzle 9 Answer: 12
Puzzle 10 Answer: 6
Puzzle 11 Answer: 2
Puzzle 12 Answer: 350
Puzzle 13 Answer: 99
Puzzle 14 Answer: 154

Puzzle 5

You say my number when you start at 0 and count by 15’s.
You say my number when you start at 0 and count by 25’s.
My number is less than 200.
My number is even.

I don't think 75 is an even number!

Originally Posted by Champ Kind

Puzzle 5

You say my number when you start at 0 and count by 15’s.
You say my number when you start at 0 and count by 25’s.
My number is less than 200.
My number is even.

I don't think 75 is an even number!

Here's a question my high school math teacher asked us:

You have 23 cubes of sugar. How can you put them all in two cups of coffee so that each cup of coffee has an odd number of sugar cubes in it (you can't break the cubes, although that wouldn't help).

After much deliberation and frustration by the class, she gave us the answer. She said, "Put 22 cubes in one cup and one cube in the other."

When we all protested that 22 is an even number, she calmly replied, "But isn't 22 an odd number of sugar cubes to put in a cup of coffee?"