Item: tExplicitArithmetic1b
Stem:
The first four terms of an arithmetic sequence are given below.
Choose the algebraic expression that represents the nth
term in this sequence.
3, 6, 9, 12, . . .
Options:
3n
n - 3
3n - 3
n + 3
3n + 3
Key:
- Observable: 1.
Score: 1;
Evidence Value: 1.
-
Student:Right! The expression you selected, 3n, is correct.
-
Teacher:The student got this item correct.
- Observable: 2.
Score: 0;
Evidence Value: 0.
-
Student:Sorry, the expression you selected, n - 3, is incorrect. The sequence in the question is: 3, 6, 9, 12,... But the expression you selected describes the sequence: -2, -1, 0, 1,...
-
Teacher:The student did not get this item right.
- Observable: 3.
Score: 0;
Evidence Value: 0.
-
Student:Sorry, the expression you selected, 3n - 3, is incorrect. The sequence in the question is: 3, 6, 9, 12,... But the expression you selected describes the sequence: 0, 3, 6, 9,...
-
Teacher:The student did not get this item right.
- Observable: 4.
Score: 0;
Evidence Value: 0.
-
Student:Sorry, the expression you selected, n + 3, is incorrect. You have found the correct recursive formula, but this is not the same as finding an expression for the nth term. The sequence in the question is: 3, 6, 9, 12,... and the expression you selected describes the sequence: 4, 5, 6, 7,...
-
Teacher:The student did not get this item right.
- Observable: 5.
Score: 0;
Evidence Value: 0.
-
Student:Sorry, the expression you selected, 3n + 3, is incorrect. The sequence in the question is: 3, 6, 9, 12,... But the expression you selected describes the sequence: 6, 9, 12, 15,...
-
Teacher:The student did not get this item right.
Metadata:
Item Node: tExplicitArithmetic1b,
Difficulty: 1.
Proficiencies: ExplicitArithmetic.