2003 AMC 8 Problems
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Timed
40:00
1.
Jamie counted the number of edges of a cube, Jimmy counted the number of corners, and Judy counted the number of faces. They then added the three numbers. What was the resulting sum?
Answer: E
Small Hint:
A cube has a fixed number of edges, corners, and faces.
Big Hint:
Add the counts for edges, corners, and faces.
Solution:
A cube has edges, corners, and faces. Adding these together yields
Thus, E is the correct answer.
2.
Which of the following numbers has the smallest prime factor?
3.
A burger at Ricky C’s weighs grams, of which grams are filler. What percent of the burger is not filler?
Answer: D
Small Hint:
First find how many grams are not filler.
Big Hint:
Compare the non-filler grams to
Solution:
We get that grams are not filler. The percentage is therefore
Thus, D is the correct answer.
4.
A group of children riding on bicycles and tricycles rode past Billy Bob’s house. Billy Bob counted children and wheels. How many tricycles were there?
Answer: C
Small Hint:
If all children had bicycles, count the wheels.
Big Hint:
Each tricycle adds one wheel compared with a bicycle.
Solution:
Let be the number of bicycles and be the number of tricycles. Then we can set up the following system of equations: Multiplying the first equation by and subtracting from the second equation, we get
Thus, C is the correct answer.
5.
If of a number is what is of the same number?
Answer: B
Small Hint:
is one fifth.
Big Hint:
Use as a stepping stone from to
Solution:
Since of the number is of the number is
Therefore of the same number is
Thus, B is the correct answer.
6.
Given the areas of the three squares in the figure, what is the area of the interior triangle?
Answer: B
Small Hint:
The square areas give the side lengths of the three squares.
Big Hint:
The side lengths form a right triangle.
Solution:
The side lengths of the squares are and These lengths form a Pythagorean triple.
Therefore, the interior triangle is right. Its area is
Thus, B is the correct answer.
7.
Blake and Jenny each took four -point tests. Blake averaged on the four tests. Jenny scored points higher than Blake on the first test, points lower than him on the second test, and points higher on both the third and fourth tests. What is the difference between Jenny’s average and Blake’s average on these four tests?
Answer: A
Small Hint:
Add Jenny’s four score differences from Blake’s.
Big Hint:
Divide the total difference by to compare averages.
Solution:
The total point difference between the two is The average of this difference is
Thus, A is the correct answer.
8.
Problems and use the data found in the accompanying paragraph and figures.
Bake Sale
Four friends, Art, Roger, Paul and Trisha, bake cookies, and all cookies have the same thickness. The shapes of the cookies differ, as shown.
• Art’s cookies are trapezoids:
• Roger’s cookies are rectangles:
• Paul’s cookies are parallelograms:
• Trisha’s cookies are triangles:
Each friend uses the same amount of dough, and Art makes exactly cookies.
Who gets the fewest cookies from one batch of cookie dough?
Art
Paul
Roger
Trisha
There is a tie for fewest.
Answer: A
Small Hint:
Same dough and thickness means larger cookie area gives fewer cookies.
Big Hint:
Compare the areas of the four cookie shapes.
Solution:
Since the cookies all have the same thickness and use the same amount of dough, the largest cookie shape produces the fewest cookies.
Art’s trapezoid has area Roger’s rectangle has area Paul’s parallelogram has area and Trisha’s triangle has area
Art has the largest cookie area, so Art gets the fewest cookies from one batch.
Thus, A is the correct answer.
9.
Art’s cookies sell for ¢ each. To earn the same amount from a single batch, how much should one of Roger’s cookies cost?
¢
¢
¢
¢
¢
Answer: C
Small Hint:
First find the total money Art earns from a batch.
Big Hint:
Use the number of Roger’s cookies from the shared dough amount.
Solution:
Art makes cookies that sell for cents each, so one batch earns cents.
The batch has square inches of dough area, and each Roger cookie has area Thus Roger makes cookies.
To earn cents from cookies, each Roger cookie should cost cents.
Thus, C is the correct answer.
10.
How many cookies will be in one batch of Trisha’s cookies?
Answer: E
Small Hint:
Trisha’s cookie area is half of Art’s cookie area.
Big Hint:
Same dough amount means half-size cookies make twice as many.
Solution:
Art’s cookie area is square inches, so the whole batch has area square inches.
Trisha’s triangular cookie has area square inches.
Therefore Trisha can make cookies per batch.
Thus, E is the correct answer.
11.
Business is a little slow at Lou’s Fine Shoes, so Lou decides to have a sale. On Friday, Lou increases all of Thursday’s prices by Over the weekend, Lou advertises the sale: “Ten percent off the listed price. Sale starts Monday.” How much does a pair of shoes cost on Monday that cost on Thursday?
Answer: B
Small Hint:
The Monday discount is taken from Friday’s increased price.
Big Hint:
Multiply the original price by then by
Solution:
On Friday, the shoes are marked up by so the listed price becomes dollars.
On Monday, the discount is taken from giving dollars.
Thus, B is the correct answer.
12.
When a fair six-sided die is tossed on a table top, the bottom face cannot be seen. What is the probability that the product of the numbers on the five faces that can be seen is divisible by
Answer: E
Small Hint:
Check the only case where the face numbered is hidden.
Big Hint:
If is hidden, the visible faces still include and
Solution:
If the face numbered is visible, then the visible product is divisible by
If the face numbered is on the bottom, then the visible faces include both and so their product is still divisible by
Every possible toss works, so the probability is
Thus, E is the correct answer.
13.
Fourteen white cubes are put together to form the figure on the right. The complete surface of the figure, including the bottom, is painted red. The figure is then separated into individual cubes. How many of the individual cubes have exactly four red faces?
Answer: B
Small Hint:
A cube has four painted faces exactly when it touches two other cubes.
Big Hint:
Separate the top cubes, bottom corner cubes, and remaining cubes.
Solution:
A cube has exactly four painted faces exactly when it is attached to exactly two other cubes.
The top cubes touch only one other cube, so they have painted faces. The bottom corner cubes touch three other cubes, so they have painted faces.
The remaining cubes each touch exactly two other cubes, so they have exactly four painted faces.
Thus, B is the correct answer.
14.
In this addition problem, each letter stands for a different digit. If and the letter represents an even number, what is the only possible value for
Answer: D
Small Hint:
Use the hundreds column after
Big Hint:
The ones column and the fact that is even force
Solution:
Since both ’s are we get that is either or Since is even, we get that
Then, we get that We also know that doesn’t carry over, since otherwise would be
Therefore, is less than and cannot be or If then which gives two letters the same digit. If then which is also not allowed.
This makes
Thus, D is the correct answer.
15.
A figure is constructed from unit cubes. Each cube shares at least one face with another cube. What is the minimum number of cubes needed to build a figure with the front and side views shown?
Answer: B
Small Hint:
Try to satisfy both views with only three cubes.
Big Hint:
A four-cube construction is shown; you only need to rule out three.
Solution:
The front view requires an L-shape with three visible positions, so at least three cubes are needed.
Suppose there were exactly three cubes. The two cubes that appear one above the other must share a face, so they have the same depth. The third cube appears beside the lower one. To share a face with either of the first two cubes, it must share the lower cube’s depth as well; otherwise it would be disconnected from both. Thus all three cubes would occupy one depth column, giving a one-column side view instead of the required L-shape.
The shown four-cube construction has both required views, so the minimum is
Thus, B is the correct answer.
16.
Ali, Bonnie, Carlo and Dianna are going to drive together to a nearby theme park. The car they are using has four seats: one driver’s seat, one front passenger seat and two back seats. Bonnie and Carlo are the only two who can drive the car. How many possible seating arrangements are there?
Answer: D
Small Hint:
Choose the driver first.
Big Hint:
After the driver is chosen, arrange the other three people in the remaining seats.
Solution:
There are options for who sits in the driver’s seat. There are options for the other front seat, and options for the first back seat.
The last person has to sit in the last seat, for a total of possible seating arrangements.
Thus, D is the correct answer.
17.
The six children listed below are from two families of three siblings each. Each child has blue or brown eyes and black or blond hair. Children from the same family have at least one of these characteristics in common. Which two children are Jim’s siblings?
Child Eye Color Hair Color Benjamin Blue Black Jim Brown Blond Nadeen Brown Black Austin Blue Blond Tevyn Blue Black Sue Blue Blond
Nadeen and Austin
Benjamin and Sue
Benjamin and Austin
Nadeen and Tevyn
Austin and Sue
Answer: E
Small Hint:
Jim’s siblings must each share eye color or hair color with Jim.
Big Hint:
The two siblings must also share at least one characteristic with each other.
Solution:
Note that Nadeen, Austin, and Sue are the only individuals who share a characteristic with Jim. We need to find which of the are completely different from the others.
Austin and Sue both have blue eyes, which makes Nadeen the odd one out. Therefore, Austin and Sue are Jim’s siblings.
Thus, E is the correct answer.
18.
Each of the twenty dots on the graph below represents one of Sarah’s classmates. Classmates who are friends are connected with a line segment. For her birthday party, Sarah is inviting only the following: all of her friends and all of those classmates who are friends with at least one of her friends. How many classmates will not be invited to Sarah’s party?
Answer: D
Small Hint:
Sarah invites vertices at distance or from her.
Big Hint:
Count the dots not within two line segments of Sarah.
Solution:
Sarah invites her friends and the classmates who are friends with at least one of her friends. In graph terms, she invites dots that are or line segments away from Sarah.
From the graph, dots are disconnected from Sarah’s component, and more dots in Sarah’s component are segments away.
Those classmates will not be invited.
Thus, D is the correct answer.
19.
How many integers between and have all three of the numbers and as factors?
Answer: C
Small Hint:
Use the least common multiple of and
Big Hint:
Count the multiples of that LCM between and
Solution:
If a number has these three numbers as factors, then their least common multiple must also divide
These numbers have the following prime factorizations:
From these values, we get that the least common multiple is
Therefore, the multiples of between and are and
Thus, C is the correct answer.
20.
What is the measure of the acute angle formed by the hands of a clock at a.m.?
Answer: D
Small Hint:
At the minute hand points at
Big Hint:
The hour hand has moved one third of the way from to
Solution:
At the hour hand will be of the way between and
Each hour represents This means the hour hand will be past
At minutes, the minute hand points to so the acute angle between the hands is
Thus, D is the correct answer.
21.
The area of trapezoid is The altitude is cm, is cm, and is cm. What is in centimeters?
Answer: B
Small Hint:
Drop perpendiculars from and to the base.
Big Hint:
Use the and right triangles.
Solution:
Drop perpendiculars from and to meeting it at and
In the left and right right triangles, and
The two side triangles have areas and The middle rectangle has area
Thus so and
Thus, B is the correct answer.
22.
The following figures are composed of squares and circles. Which figure has a shaded region with largest area?
only
only
only
both and
all are equal
Answer: C
Small Hint:
Figures and leave the same shaded area.
Big Hint:
For compare with
Solution:
In figure the shaded area is the area of a by square minus a circle of radius so it is
Figure is made of four copies of figure with half the side length, so each copy has one-fourth the area and the total shaded area is also
In figure the circle has radius and the inscribed square has diagonal so its area is The shaded area is
Since we have so figure has the largest shaded area.
Thus, C is the correct answer.
23.
In the pattern below, the cat moves clockwise through the four squares and the mouse moves counterclockwise through the eight exterior segments of the four squares.
If the pattern is continued, where would the cat and mouse be after the th move?
Answer: A
Small Hint:
The cat repeats every moves.
Big Hint:
The mouse repeats every moves; use the remainders of
Solution:
The cat’s position repeats every moves, and the mouse’s position repeats every moves.
Since the cat is in the same position as after the rd move: the lower right square.
Since the mouse is in the same position as after the th move: the left side of the lower left square.
Thus, A is the correct answer.
24.
A ship travels from point to point along a semicircular path, centered at Island Then it travels along a straight path from to Which of these graphs best shows the ship’s distance from Island as it moves along its course?
Answer: B
Small Hint:
Along the semicircle, the distance from is constant.
Big Hint:
On the straight segment, the ship first gets closer to then farther away.
Solution:
Every point on the semicircular path from to is the same distance from the center so the graph starts horizontally.
On the straight path from to the ship first gets closer to and then farther away from
Only graph starts flat and then decreases before increasing.
Thus, B is the correct answer.
25.
In the figure, the area of square is The four smaller squares have sides cm long, either parallel to or coinciding with the sides of the large square. In and when is folded over side point coincides with the center of square What is the area of in square centimeters?
Answer: C
Small Hint:
Let be the midpoint of
Big Hint:
Folding makes the distance from to equal the distance from to
Solution:
The side length of is cm, since
We also know that the distance from to is since it is the sum of the side lengths of unit squares.
Finally, the distance from to is the same as the distance from to which is
Now, we can find which is
Therefore, the area of is
Thus, C is the correct answer.