EP3397
Mathological Liar Grade 4
Object of the Game
In each round, players are given a case
to solve. There are four suspects in
each case. One or more of the suspects
is guilty. Each player reads his or her
suspect’s alibi. If the math or reasoning
in the suspect’s alibi is correct, he or she
is innocent. If the math or reasoning is
incorrect, that suspect is lying and is
guilty of the crime.
Before You Play
Do not shuffle the cards. Each round
consists of four cards. When you take a
round out of the box to play, make sure
the case numbers on the cards match.
When you are done with a round, place
the used cards in a group at the back of
the box. Before you begin, decide how
many rounds you will play, or set a time
or point limit for the game. Then, gather
scratch paper, a pencil, and, if needed,
a calculator for each player. Decide who
will be the scorekeeper and keeper of
the Answer Key.
Directions (2 to 4 players)
1. Hand out a Case Card to each player.
There are four cards for each case, each
with a different alibi on the back. (If
there are only two players, give each
player two Case Cards.)
2. Have one player read the case on the
back of the card out loud to the group.
3. Have each player read his or her
suspect’s alibi silently. Each player will
then write down whether or not his or
her suspect is guilty or innocent.
4. One by one, each player reads his
or her alibi out loud to the group. The
player must then state whether the
suspect is guilty or innocent, and why.
The person with the Answer Key reveals
the answers. Each player receives one
point for correctly stating whether his
or her suspect is innocent or guilty. If
the suspect is guilty, the player can earn
an extra point for correctly giving the
reason why the suspect is guilty (why
the math is incorrect). The scorekeeper
writes down each player’s score.
5. The first person to reach the point
goal, or the person who has earned
the most points at the end of the set
number of rounds or at the set time
limit, wins the game!
Alternate Play
Have each player read his or her
suspect’s alibi out loud to the group. As
a group, players determine whether or
not the suspect on each card is guilty or
innocent, and why. The person with the
Answer Key reveals the answer. Each
player whose suspect is innocent earns a
point. The player with the most points at
the end of the game wins!
Individual, Small-Group, and
Whole-Class Practice
Put each four-card set of Case Cards in
an envelope and place in a math center.
Challenge students to individually
work through the alibis on each case
to determine who is the guilty party.
Provide an Answer Key for self-checking.
Encourage students to work through
the cards in pairs or small groups and
discuss their answers with each other.
For a whole-class activity, project the
cards on a screen to jumpstart math
lessons. Read the case aloud, and then
project the four alibis at the front of the
room. As a class, have students help
determine who is the culprit.
Answer Key
Case #1: Mr. Seed and Miss Robin did it. Mr. Seed said his
wife bought 16 sacks of seed over 3 weeks. However,
8 + 6 + (6 - 2) = 18 sacks. Miss Robin said there were 11
more purple than yellow houses. However, 19 - 7 = 12.
Case #2: Nina did it. 1,000 – (300 + 250) = 450. Nina said
she needed 550 more.
Case #3: Mrs. Brown and Larry did it. Mrs. Brown said
1 teaspoon was more than 1 teaspoon. It is actually less.
8
4
Larry said 15 of the gold was more than 13 of the gold, but it
is less.
Case #4: Silvio and Lucy are guilty. Silvio says 14 = .4,
but 14 = .25. Lucy says that 15 is not equal to .2, but 15
does equal .2.
Case #5: Laura is guilty. If she had the number 90, she
would have to go to the station with 9 yellow balloons,
not 9 blue balloons.
Case #6: Joy did it. 90 + 61 = 151, so she should have put
a 1 in the hundreds place, a 5 in the tens place, and a 1 in
the ones place.
Case #7: All 4 of the suspects did it! Will said 8 × 7 = 54,
but 8 × 7 = 56. Nan said 12 × 7 = 94, but 12 × 7 = 84. Ron
said 30 × 8 = 230, but 30 × 8 = 240. Liz said 12 × 5 = 70,
but 12 × 5 = 60.
Case #8: Lee did it. He said 9 × 12 = 100, but 9 × 12 = 108.
Case #9: Chef Veggie did it. The chef said 160 ÷ 4 = 30,
but 160 ÷ 4 = 40.
Case #10: R.U. Real did it. 126 ÷ 3 = 42 marshmallow
ghosts, not 46.
Case #11: Sly and Shifty did it together. Sly said .4 = 4%,
but .4 = 40%. Shifty said .25 = 250%, but .25 = 25%.
Case #12: Haley did it. She said 50% is less than .06, but
.06 is only 6%. That is much less than 50%.
Case #13: Farmer Green did it. He said that 60 ÷ 12 = 5
and 12 ÷ 5 = 60. That’s not correct. Since 60 ÷ 12 = 5,
12 × 5 = 60.
Case #14: Dina did it. She said if 9 × 7 = 63, then
9 ÷ 7 = 63. That is not correct. If 9 × 7 = 63, then 63 ÷ 7 = 9.
Case #15: Nasty and Shady did it. Nasty said there were
about 1,000 jelly beans, but he should have estimated 30
times 50 = about 1,500. Shady said there were about 3,600
jelly beans in the jar, but he should have estimated 30 times
60 = about 1,800 jelly beans.
Case #16: Keith did it. He said he heard the rules about
200 times. If you round 9 up to 10 and multiply it by 16, it
only is about 160.
Case #17: Neither James nor Laura went stargazing.
James said a hexagon has 4 sides; it really has 6. Laura said
she made a parallelogram because squares and rectangles
are boring. But both those shapes ARE parallelograms.
Case #18: Amy is the polygon pirate. A polygon is a
closed shape. A horseshoe is an open shape.
Case #19: Jenna did it. A circle is a 2-dimensional shape.
Only 3-dimensional shapes were taken.
Case #20: Ming did it. A square is a plane shape. A
6 × 6 × 6 shape would be a cube.
Case #21: Cara did it. She said all triangle pairs will look
alike no matter how many times you turn one of them. An
isosceles triangle only has 2 equal sides. You would have
to turn it 360°, or 3 times, to make it look like its partner.
Case #22: Gail and Wayne did it. Gail said she needs
3 more quarter turns to make the rectangle look like
the other one. Actually, it only needs 1 more turn. If you
turn a rectangle on its side 2 times, it will look the way it
started. Wayne said a parallelogram only needs 2 quarter
turns to make it look like the other. A parallelogram needs
4 quarter turns.
Case #23: They all did it. The drummer and the trumpet
player said their music measures weren’t patterns. They
are. The guitarist said he continued the pattern, but he
didn’t follow it. The tambourine player said his music
measure was a great pattern. However, the CAB broke the
pattern.
Case #24: Bani is the beady bandit. Her pattern was
broken when she said 3 white, 2 red, 1 black. It should
have been 3 white, 2 black, 1 red.
Case #25: Lynn is the bagel bandit. Adding 37 singleand double-digit numbers together would take more
than a minute. Lynn would need a pencil and paper.
Case #26: Ben did it. He shouldn’t need a calculator to
figure it out. He could multiply 7 × 2 in his head and add
three zeros.
Case #27: Nick and Grace did it. Nick’s fence should be
measured in yards, not feet. The space between Grace’s
signs should be measured in feet, not inches.
Case #28: Josh did it. He said 35 in. = to 3 ft, but 3 ft =
36 in.
Case #29: Liz locked the captain in his cabin. She said
1,000 mm = 100 m, but 1,000 mm = 1 m.
Case #30: Leo and Tina did it. Leo said 1 lb = 32 oz, but 1
lb = 16 oz. Tina said 30,000 oz = 1 ton, but
1 ton = 32,000 oz.
Case #31: Phil did it. 1 dg of flour = 10 cg of flour, not
100 cg.
Case #32: Gina did it. She said 1 pint = 4 cups, but really
1 pint = 2 cups.
Case #33: Becky did it. She said 1 gallon = 3 quarts.
One gallon actually = 4 quarts.
Case #34: Luke and Maura did it. Luke said the area of
the rectangle was 44 ft, but it’s actually 40 sq ft. Maura
used square feet for the perimeter and feet for the area. It
should be the opposite.
Case #35: Oliver is taking the bones. He said you can
find the area of a triangle by multiplying the base times
the height. The actual formula is: 12 b × h.
Case #36: Mr. Sparks is lying. No one took his silver. He
said 5 half dollars were worth 30 dimes. That’s a lie. Five
half dollars are worth $2.50. Thirty dimes are worth $3.00.
Case #37: Pickpocket Parker is lying. Five nickels and
2 pennies are worth 27¢, not 47¢.
Case #38: Ms. T did it. The original two quarters, 3
pennies, and 4 nickels did equal 9 coins and 73¢. She took
2 quarters, 3 pennies, and 4 dimes. That equals 9 coins
and 93¢, which is 20¢ too much.
Case #39: Mike and Marcus did it. Each only put a $5 bill
in the basket, but each owed about $6.00.
Case #40: Lonnie lost the loot. He gave the lady more
than $5.00 in change. He should have given her between
$4.00 and $5.00 in change.
Case #41: Brian lost the minutes. He said he watched for
70 minutes, but he actually watched for 80 minutes.
5:05 – 3:45 = 1 hour and 20 minutes, or 80 minutes.
Case #42: Dennis and Fred messed with the bells.
Dennis said his workers got 15 extra minutes for lunch, but
they actually got 15 minutes less. Fred said that the bells
rang at 6:45 and at 7:15. That means 30 minutes passed
between the bells ringing, not 45 minutes.
Case #43: Miss Pansy did it. She said 17 – 19 = 2, but
17 – 19 = -2.
Case #44: Yosi is fooling around with the number line.
If the problem is 1 – 7, the arrow should point to the sixth
mark to the left of 0, not the seventh mark.
Case #45: Stan and Drew did something to the bag of
pearls. Stan said because he went first, he would most
likely pull the pink pearl. But he only had a 1 in 100 chance
of pulling that pearl. Drew said his chances were better
because 2 colored pearls and no white pearls had already
been pulled. But that lowered his chances. It was less
likely, not more likely.
Case #46: Justin rigged the contest. He said that it was
more likely that he would pull the striped fish. There was
only a 1 in 100 chance he would do that. It was least likely
that he would pull the striped fish.
Case #47: Simon helped Tommy. To predict the number
of times he would pick a red ball, he should divide the
number of pulls by 14 . So although he would likely pull red
once if he pulled 4 times ( 14 × 4), if he pulls 40 times it’s
likely red will be pulled 10 times ( 14 × 40).
Case #48: Piper is the Happy Camper. She said 5 of the
5 or
20 cabins received flowers from her. That would be a 20
1 chance, not a 1 chance like she said.
4
5
Case #49: Vivi has the Golden Triangle. She said 36, 54,
and 72 are all multiples of 4. 54 is not a multiple of 4. All
three numbers are multiples of 9. (9 × 4 = 36, 9 × 6 = 54,
and 9 × 8 = 72.)
Case #50: Stella, Henry, and Aiden all did it. For Stella,
the numbers 77, 42, and 14 are multiples of 7, but 12 is
not. For Henry, the numbers 30, 54, and 72 are multiples
of 6, but 35 is not. For Aiden, the numbers 55, 66, and 22
are multiples of 11, but 46 is not.
EP3397 Mathological Liar, Gr. 4 © Highsmith LLC