EIGHTH GRADE TRAINING GUIDE

1994 Mathematics Rubric - Eighth Grade


FORM F

5. Triangle ABC is a right triangle, with AB = 5 and CB = 12. Triangle ABD is an isosceles triangle with AB = AD. What is the length of CD? Explain how you arrived at your answer.

ITEM SCORE SCALE

0 Answer is unresponsive, unrelated, or inappropriate. Answer contains nothing correct.
1 Answer provides the number "8", with no explanation or incorrect explanation. Or, answer other than "8" is given, in conjunction with a partially correct explanation.
2 Answer provides the number "8", with an explanation or work shown which contains an error and/or an omission, or, answer contains a complete explanation or complete work shown but the length of CD is incorrect due to a computation error.
3 Answer provides the number "8", with a complete and correct explanation. The explanation must contain verbiage as well as work shownm, and must use the Pythagorean approach.


STUDENT RESPONSES

QUESTION

5. Triangle ABC is a right triangle, with AB = 5 and CB = 12. Triangle ABD is an isosceles triangle with AB = AD. What is the length of CD? Explain how you arrived at your answer.


STUDENT RESPONSE NUMBER ONE

17

Add AB and CB length

RUBRIC SCORING

0 --Answer of "17" is incorrect, and explanation is incorrect.


STUDENT RESPONSE NUMBER TWO

8

RUBRIC SCORING

1 -- A correct answer of 8 is given, with no explanation.


STUDENT RESPONSE NUMBER THREE

8

The other measurements are twice the amount of centimeters. CD = 4 cm so I doubled it, which equals 8.

RUBRIC SCORING

2 -- A correct value of 8 is given. The explanation is correct but omits a discussion of use of the Pythagorean theorem.


STUDENT RESPONSE NUMBER FOUR

8

5 squared + 12 square = hy6potonuse then subtract 5 from the answer.

RUBRIC SCORING

2 -- A correct answer of 8 is given, with an explanation which contains an error (5 squared + 12 squared = the square of the hypotenuse). Also, there is an omission as the length of the hypotenuse is never stated.


STUDENT RESPONSE NUMBER FIVE

8

You can calculate the length of side AC by using the formula for the hypotenuse. Then you subtract AD (AD = 5) from AC.

RUBRIC SCORING

3 -- Answer is correct, with a complete and correct explanation.