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Problem Solving for the 21st Century: Built for the NY NextGen Standards

If a Bear Walks Into the Woods

Researchers in the Denali National Park in Alaska are using GPS collars to study the habits of wild grizzly bears in the park. Granny is a mother bear who researchers have been following for over 10 years. The locations on the grid below are the specific locations where Granny spent significant time during the previous day. Researchers wanted to use the data collected to approximate how far this grizzly bear may have traveled in a given day. Granny started and ended her day at location (12, -9) and moved from location to location in alphabetical order, as indicated on the grid.

Provide researchers with a clear explanation of your calculations for how far this grizzly may have traveled.

Note: One unit on the grid represents 500 ft.

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instructional
Domain:
Standard:
Mathematical Practices:
  • MP.2
  • MP.2

    Reason abstractly and quantitatively.

  • MP.4
  • MP.4

    Model with mathematics.

  • MP.6
  • MP.6

    Attend to precision.

  • MP.7
  • MP.7

    Look for and make use of structure.

View all Grade 8 tasks

More Accessible Version

Researchers in the Denali National Park in Alaska are using GPS collars to study the habits of wild grizzly bears in the park. Granny is a mother bear who researchers have been following for over 10 years. The locations on the grid below are the specific locations where Granny spent significant time during the previous day. Researchers wanted to use the data collected to approximate how far this grizzly bear may have traveled in a given day. Granny started and ended her day at location (12, -12) and moved from location to location in alphabetical order, as indicated on the grid.

Provide researchers with a clear explanation of your calculations for how far this grizzly may have traveled.

Note: One unit on the grid represents 100 meters.

Printer-Friendly Overhead △

More Challenging Version

Researchers in the Denali National Park in Alaska are using GPS collars to study the habits of wild grizzly bears in the park. Granny is a mother bear who researchers have been following for over 10 years. The locations on the grid below are the specific locations where Granny spent significant time during the previous day. Researchers wanted to use the data collected to approximate how far this grizzly bear may have traveled in a given day. Researchers are also trying to determine the total area of the territory Granny seems to utilize.

Granny started and ended her day at location (12, -9) and moved from location to location in alphabetical order, as indicated on the grid.

Provide researchers with a clear explanation of your calculations for how far this grizzly may have traveled and the area of her territory.

Note: One unit on the grid represents 500 ft.

Printer-Friendly Overhead ▢

Plan

Underlying Mathematical Concepts

  • Solving for unknowns in equations
  • Scaling
  • Pythagorean Theorem

Possible Problem-Solving Strategies

  • Area model
  • Apply the Pythagorean Theorem
  • Similar figures
  • Guess and check

Formal Mathematical Language and Symbolic Representation

  • Average
  • Constant rate
  • Coordinate plane
  • Coordinate point
  • Exponent
  • Hypotenuse
  • Legs
  • Perfect square
  • Pythagorean Theorem
  • Pythagorean triple
  • Radicals
  • Right angle
  • Right triangle
  • Scale
  • Similar figures
  • Square root
  • Substitution
  • Sum
  • Unit rate
  • x-axis
  • y-axis

Teacher Notes:

Possible questions to pose during the launch of this task:

  • How can you draw a right triangle between each pair of points?
  • Why can grid lines be used to find the lengths of the legs of the triangle but not the hypotenuse?
  • Between each pair of points, what’s a distance that’s too high, what’s a distance that’s too low?

Possible misconceptions that students may encounter:

  • Students may forget to convert the units on the grid to feet.
  • Students may try to count the squares between each point and use this as the distance.
  • Students may think the sum of the 2 legs is equal to the length of the hypotenuse.
  • Students might think that the sum of the squares of the 2 legs is equal to the hypotenuse.

Suggested Materials

Engagement Image:

Teachers may project the image below to launch this task for their students, define nouns, promote discussion, access prior knowledge, and inspire engagement and problem solving.

Click image to enlarge

Task-Specific Evidence

This task requires students to find the diagonal distance between points on a coordinate plane, using the Pythagorean Theorem, to determine how far a bear travels throughout its day.

Printer-Friendly Planning Sheet
Printer-Friendly Exemplars Rubric

Possible Solutions

  • Task Solution (active tab)
  • More Accessible Solution
  • More Challenging Solution
Task Solution

Granny traveled at least 42,900 feet or 8.125 miles.

The horizontal and vertical distance between points makes the legs of a right triangle between each set of points. Students may see the triangles on the exterior of the perimeter as shown and/or on the interior of the perimeter.

Area Model of the Pythagorean Theorem
The relationship between the sides can be modeled on grid paper or using an open area.

 A to BB to CC to DD to EE to A
Longer Leg Square
(square units)
24•24=57612•12=14415•15=22512•12=14415•15=225
Shorter Leg Square
(square units)
7•7=495•5=258•8=649•9=815•5=25
Hypotenuse Square 
(square units)
576+49=625144+25=169225+64=289144+81=225225+25=250
Hypotenuse Length 
(units)
2513171515.8

Apply the Pythagorean Theorem

 A to BB to CC to DD to EE to A
Length of Longer Leg 
(units)
2412151215
Length of Shorter Leg
(units)
75895
Pythagorean Theorem`sf24^sf2+sf7^sf2=c^sf2`
`sf576+sf49=c^sf2`
`sf625=c^sf2`
`sf12^sf2+sf5^sf2=c^sf2`
`sf144+sf25=c^sf2`
`sf169 =c^sf2`
`sf15^sf2+sf8^sf2=c^sf2`
`sf225+sf64=c^sf2`
`sf289=c^sf2`
`sf12^sf2+sf9^sf2=c^sf2`
`sf144+sf81=c^sf2`
`sf225=c^sf2`
`sf15^sf2+sf5^sf2=c^sf2`
`sf225+sf25=c^sf2`
`sf250=c^sf2`
Hypotenuse 
(units)
2513171515.8

Similar Figures (for point D to E)
The length of the hypotenuse (c) has to be greater than the length of each leg (a and b).

Guess and Check

The length of the hypotenuse (c) has to be greater than the length of each leg (a and b).

Point A to B

Longer Leg(a)a2Shorter Leg (b)b2Hypotenuse(c)c2`a^2+b^2=c^2`Accuracy
2457674925625576+49=625Correct

Point B to C

Longer Leg(a)a2Shorter Leg (b)b2Hypotenuse(c)c2`a^2+b^2=c^2`Accuracy
1214452513169144+25=169Correct

Point C to D

Longer Leg(a)a2Shorter Leg (b)b2Hypotenuse(c)c2`a^2+b^2=c^2`Accuracy
1522586416256225+64≠256Too low
︙︙︙︙17289225+64=289Correct

Total Distance Traveled:

25 + 13 + 17 + 15 + 15.8 = 85.8 units

85.8 units x 500 feet per unit = 42,900 feet

More Accessible Solution

Granny traveled at least 8,000 meters.

 A to BB to CC to DD to A
Length of Longer Leg
(units)
22
Vertical line
16
Horizontal line
1524
Length of Shorter Leg
(units)
N/AN/A87
Pythagorean TheoremN/AN/A152 + 82 = C2
225 + 64 = 289
242 + 72 = C2
576 + 49 = 625
Hypotenuse 
(units)
22161725

22 + 16 + 17 + 25 = 80 units
80 units × 100 meters per unit = 8,000 meters

More Challenging Solution

Granny traveled at least 42,900 feet and seems to utilize an area of approximately 119,375,000 feet2. Students' answers will vary for where Granny’s additional stop may have been.

See the solution to the original version of the task for possible strategies to find the distance Granny traveled.

The area of Granny’s territory can be inscribed by a larger rectangle using the right triangles that were used to find the distance traveled in a day. The area of the triangles and smaller rectangle shown can be subtracted from the area of the larger rectangle to find the area of Granny's territory.

Area of the larger rectangle: 27 × 29 = 783 units2

 Triangle ABTriangle
BC
Triangle
CD
Triangle
DE
Triangle EASmaller rectangle
Dimensions7 x 245 x 128 x 159 x 125 x 155 x 8
Area84 units230 units260 units254 units237.5 units240 units2

783 – (84 + 30+ 60 + 54 + 37.5 + 40) = 477.5 units2

477.5 × 5002 = 119,375,000 feet2

Possible Connections

  • Granny traveled 42,900 feet, which is the same as 8.125 miles.
  • The distance Granny traveled between each point has to be greater than the length of the longer leg but less than the sum of the two legs.
  • By traveling along the hypotenuse, Granny is traveling a shorter distance than traveling along the legs.
  • The measurements for a right triangle with all whole number dimensions, such as a 3-4-5 triangle are Pythagorean Triples.
  • If Granny spent 10 hours traveling, then she was moving less than 1 mile per hour.
  • Relate to a similar task and state a math link.
  • Solve more than one way to verify the answer.

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