Hands-on math!

Washington State Math Olympiad
Hints and Solutions
2012 Grade 5 Geometry

Problem
Hint
1) Sarah is making tickets for the school dance. What is the maximum number of 1 1/2 x 2 1/2 inch tickets she can cut from a 8 1/2 x 11 inch sheet of card stock paper? You can't just compute the area of the sheet of paper and divide by the area of a ticket because the tickets don't fit evenly on the paper. There will be waste. You can put the tickets (a)vertical (long side on the 8 1/2 dimension) or (b) horizontal (long side on the 11 dimension).
(a) vertical
1. Compute how many tickets can be put along the 8 1/2 inch side with their 2 1/2 inch width = _____.
Round down to _____ tickets.
2. Compute how many tickets can be put along the 11 inch side with their 1 1/2 inch height = _____.
Round down to _____ tickets.
3. Multiply these two numbers to get the number of tickets = _____ tickets.
(b) horizontal
1. Compute how many tickets can be put along the 11 inch side with their 2 1/2 inch width = _____ tickets.
2. Round down to ____ tickets.
3. Compute how many tickets can be put along the 8 1/2 inch side with their 1 1/2 inch height = ______ tickets.
4. Round down to _____ tickets.
5. Multiply these two numbers to get the number of tickets = _____ tickets.
The answer is the larger of these two numbers = _____
2) An isosceles trapezoid has a line of symmetry. Three of the vertices of the isosceles trapezoid are
(1, 6 ), (3, 2), and (7, 2) as shown.
The fourth vertex has whole number coordinates. What are the coordinates of the fourth vertex?
1. Draw the 2 sides that are given by the 3 points.
2. One of the bases of the trapezoid is the line from point 2 to point 3.
3. Draw a line from point 1 parallel to the base you drew.
4. Locate a point on that line that makes the trapezoid isosceles (sides other than the bases are equal).
5. Draw the 4th side. It should be symmetric with the other side.
6. The coordinates of point 4 are _______.

Problem
Hint
3) The first figure is a square with side length 3 units. The second figure is obtained from the first by replacing each middle third of a side with three sides of a square. The third figure is obtained from the second by replacing each middle third of a side with three sides of a square. What is the area of the third figure? The third figure is not accurately drawn, it is there to help you visualize.
Express your answer as a mixed number.
Tough problem! ... but let's get started:
1. The area of the first square = _____
2. The second figure adds 4 squares whose sides are 1/3 of the big square sides. The added sides are ____ units, The individual squares area is ____ units, and 4 of them add _____ sq. units.
3. The sides of the little squares in the 3rd figure are 1/3 of the sides in the second figure = _____ units. Their area is _____ sq. units
4. Count the number of edges in the second figure. There are ____ of them.
5. If you look close, each of the edges in the second figure has a little square on it in the 3rd figure. There is one for each edge, so this adds _____ sq. units to the total area.
6. Now, add the area of the first square ____, the added area of the small squares in the second figure _____, and the added area from the previous step = _____ sq. units.

4) At twelve noon the angle between the hour and minute hands on an analogue clock is 0 degrees. What is the angle between the hands on the clock at 12:30 pm? (30 minutes later)
This problem isn't as easy as it sounds, because as the minute hand moves from 0 to 30 minutes (half a revolution), the hour hand is moving also.
1. For an hour, the hour hand moves through this fraction of a revolution = _____ degrees.
2. For half an hour it moves half that much = _____ degrees.
3. The angle between the hour hand at the above angle and the minute hand is _____ degrees.
5) To find the area of parallelogram ABCD, Drew draws the perpendicular segments DS and BT. He does some measuring. To the nearest tenth of a centimeter BC = 7 cm, CT = 6.7 cm, BS = 5 cm, and DS = 2.1 cm. If he has enough information to compute the area of parallelogram ABCD, then compute the area to the nearest tenth of a square centimeter. If he needs to make more measurements, list the segments he needs to measure. The area of a parallelogram is base x height.
1. The base of the parallelogram is AB or DC.
2. The height is DS = ____ cm.
3. Use the TC length and the SB length to find the length of AB = ______
4. Multiply the two to get the area = ______.