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NFES
Puzzler Archive
All the puzzles we use have
been solved by third and fourth graders.
We encourage parents to get involved.
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Table Puzzler
Puzzler:
There are 6 places set at each table
for the big outdoor party. All the tables and chairs have
4 legs each, and all together the tables and chairs have a
total of 196 legs. If there is one place set for each person
who will attend, how many people are expected to come to the
big party?
Solution:
42 people are expected to come to the big
party.
Each table has 6 chairs, so there are a total of 7
x 4 = 28 legs at each table. (Don't forget to count the table
legs!)
So
196 legs ÷ 28 legs at each table = 7 tables.
Therefore, 7 x 6 = 42 guests who are expected to come
to the party.
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Train Puzzler
Puzzler:
Two trains are 200 miles apart and heading
toward each other on the same track. Each train is traveling
50 miles per hour. A fly leaves one train and speeds directly
along the track toward the other train at 75 miles per hour.
When it reaches the second train, it immediately turns and flie
s back to the first train. The fly keeps repeating this process
until the trains smash together and crush the fly between them.
How many miles did the
fly travel?
Solution:
This more advanced problem is appropriate
for 6th graders.
We want to know the total distance that the fly covers, so let's
use Time = Distance / Rate to solve the problem. We already
know the fly's rate of flight. If we can find the time that
the fly spends in the air, we can figure out how far it travels.
Ignore the fly for a minute and concentrate on the trains. The
first train is traveling at 50 miles/ hour and the second train
is going 50 miles/ hour, so they are approaching each other
at 50 miles/ hour + 50 miles/ hour = 100 miles/ hour. Now we
know the rate at which the trains are closing in on each other
and their distance apart (200 miles), so we can find the time
until they crash:
Time = Distance / Rate
= (200 miles) / (100 miles/ hour)
= 2 hour.
The fly spends the same amount of time traveling as the trains.
It goes 75 miles/ hour, so in the 2 hours the trains take to
collide, our hapless fly will travel 150 miles before being
crushed.
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Egg Puzzler
Puzzler:
The December puzzler is an extension
of the November puzzler. Chris has a basket of eggs for sale.
He sells half the eggs plus half an egg to Maria. Then he
sold half the remaining eggs plus half an egg to Ai-Ling and
finally, he sells half the remaining eggs plus half an egg
to Jermaine. At the end of the three sales, Chris is out of
eggs. The funny thing is that Christopher never had to break
an egg. How many eggs did Chris start with? Does only one
solution exist? (This is a difficult 3rd grade problem.) No
eggs are hard-boiled or cut in half!
Solution:
There is only one solution and the answer is 7 eggs.
In this case, Maria buys ½ of Chris's
eggs + ½ of 1 egg. Ai-Ling buys ½ the eggs left
+ ½ of 1 egg, and Jermaine buys ½ of the remaining
eggs + ½ of 1 egg. No eggs are broken and Chris has
no eggs left after the three sales.
If Chris has 7 eggs for sale, Maria buys ½
of 7 eggs (3 ½ eggs) and ½ of 1 more egg. 3
½ eggs + ½ egg = 4 eggs. Now, Ai-Ling buys ½
of the remaining eggs (7 - 4 = 3), so ½ of 3 eggs is
1 ½ eggs.
Ai-Ling also buys ½ of 1 egg for a total of 2 eggs.
(1 ½ = ½ + 2)
To sum up so far, Maria has bought 4 eggs, Ai-Ling has bought
2 eggs leaving one egg for Jermaine, so 6 of 7 eggs have been
sold leaving 1 egg.
Finally, Jermaine buys ½ of the remaining eggs + ½
of 1 egg. Since 1 egg remains, ½ of the remaining eggs
is ½ of 1 egg. Jermaine, like all the others, also
buys ½ of 1 egg. Since there is only 1 egg left, Jermaine
has bought the last egg.
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Egg Puzzler
Puzzler:
Christopher had a basket of eggs for
sale. He sold half the eggs plus one egg to Maria. Then he
sold half the remaining eggs plus one egg to Ai-Ling. Finally,
he sold half the remaining eggs plus one egg to Jermaine.
The funny thing is that Christopher never had to break an
egg. How many eggs did Christopher Start with? [What's
the lowest number that Christopher could could start with?]
Solution:
The answer to the November Puzzler
is 14.
The key is to find an even number that, when divided by 2,
has an odd answer. For example, 6 divided by 2 = 3. Then,
just do the math. 14 divided by 2 = 7.
Maria buys half of Chris's eggs + 1: 7 + 1 = 8. 14 - 8 = 6
eggs remaining.
Ai-Ling buys ½ of the remaining eggs +1: 6 divided
by 2 = 3: 3+ 1 = 4 eggs sold to Ai-Ling.
Jermaine buys ½ of the remaining eggs + 1: (Maria bought
8, Ai-Ling bought 4 which leaves 2 eggs.) 2 divided by 2 =
1: 1 + 1 =2, so Jermaine buys 2 eggs.
Between the three, they have bought 14 eggs.
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Digit Puzzler
Puzzler:
Take the number of your fingers multiplied
by the number of your toes divided by one half. Then add it
to the number of months in a year. What is the total?
Solution:
Assuming you have all your fingers
and toes and no extras, 10 fingers X 10 toes = 100. 100 divided
by one half = 200. 200 + 12 months = 212.
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Muffin
Puzzler
Puzzler:
Goldilocks's grandmother hands a basket
of freshly made peanut-butter-and -chocolate muffins to Goldilocks
and says, "These are for you, darling, but they just
came out of the oven and need to cool before you can eat them.
Please set them outside on the porch. You can enjoy them later."
Goldilocks thanks her grandmother and carefully places the
basket on the front porch of their forest home. She then goes
inside to take a nap while the muffins cool.
Three bears stroll by the cottage and smell the wonderful
aroma of the muffins. They follow the smell right to Goldilocks's
front porch and smile when the see both the nameplate on the
door and the basket of muffins. Papa Bear approaches the basket
first and eats exactly ¼ of the muffins.
"Mmm," groans Papa Bear, "These are yummy."
Next Mama Bear eats exactly 1/3 of the remaining muffins.
"You are right Papa, "she declares. "These
are yummy."
Finally Baby Bear goes to the basket and eats exactly ½
of the muffins left by Mama Bear. He licks his lips and says,"Mmm,
much better than porridge."
The three bears pat their full tummies; smile contentedly
at one another and continue their walk through the forest.
When Goldilocks awakens from her nap, she immediately runs
to the porch to grab the basket of muffins. She is startled
to discover that only 3 muffins remain in the basket. "What
happened to all the muffins?" she exclaims. "I know
there were more than 3 in this basket when I put it here.
I wonder how many muffins were in the basket to begin with?"
Use the information in the story to help Goldilocks determine
how many muffins were in the basket. If Papa Bear took ¼
of the original muffins, Mama Bear took 1/3 of what he left,
Baby Bear took ½ of what remained, and only 3 muffins
are left in the basket, how many muffins were in the basket
when Goldilocks first put them on the porch?
Solution: The
easiest way to solve this problem is to use the smallest common
multiple for the fractions 1/4, 1/3, and 1/2. Conveniently,
this happens to be 12. 4, 3, and 2 all go into 12.
So, if Papa Bear ate exactly 1/4 of the total,
he ate 3 brownies. This leaves 9 brownies. Mama Bear eats
exactly 1/3 of the remaining 9, so Mama Bear also ate 3 brownies
leaving 6 brownies. Baby bear ate exactly 1/3 of the 6 remaining
brownies, so Baby Bear also at 3 brownies.
Another way to look at the problem is with
a 1 X 12 array, and then divide the array into 4 equal parts.
Now remove or color in the parts of the
whole that each of the bears eats. Papa Bear ate 1/4 of the
whole or all of the "A" brownies leaving the following:
Mama Bear ate 1/3 of the remaining brownies
or all of the "B" brownies which leaves the following:
Now Baby Bear eats 1/2 of the remaining brownies
or 1/2 which means he ate the "C" brownies. This
leaves the "D" brownies for Goldilocks and the bears
have their revenge!
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Coin
Puzzler
Puzzler: Kelly has 12 coins
in her pocket. One-third of the coins are dimes. She has twice
as many dimes as nickels. The rest of the coins are pennies.
How much money does Kelly have in her pocket?
Solution:
There are 12 coins in all. One-third of the
coins are dimes. If we divide the 12 coins into three equal
groups or thirds, we find that each group has four coins. Thus
there are 4 dimes which equal $0.40.
There are half as many nickels as dimes. This
means there must be two nickels which equal $0.10. The rest
of the coins are pennies. Since we have 6 coins so far (4
dimes + 2 nickels), we now know there are 6 pennies which
equal $0.06. By adding up the totals for each set of coins
($0.40 + $0.10 +$0.06) we get an answer of $0.56.
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Square
Puzzler
Puzzler
Click on this link for PDF.
Solution
Click on this link for PDF.
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