Difficulty: Hard

Average Score: 41%

Which of the following best explains what Colin is doing?

Rationale

Colin is skip-counting by 10s and adding on.

Colin's method involves counting in increments of ten and then performing additional calculations, which aligns perfectly with the definition of skip-counting. This technique allows him to efficiently navigate through numbers while also incorporating extra values as needed.

A (Decomposing 77 into 10s and 1s) YOUR ANSWER

Decomposing a number involves breaking it down into its constituent parts, such as separating 77 into 70 (10s) and 7 (1s). While this process is related to understanding place value, it does not accurately describe Colin's approach if he is actively counting in a sequence rather than merely breaking a number apart.

B (Counting on from a multiple of 5 and 11) YOUR ANSWER

Counting on from multiples of 5 and 11 suggests a specific pattern not directly indicated in the question. Colin's actions do not involve focusing on these particular multiples, which would lead to a different counting strategy unrelated to the task of skip-counting by 10s.

C (Skip-counting by 10s and adding on) CORRECT

This choice correctly identifies Colin's method. Skip-counting by 10s involves adding ten repeatedly, which is a common technique in mathematics to count efficiently. The addition part indicates that he is not just counting but also performing calculations to reach a target number.

D (Finding doubles greater than 55) YOUR ANSWER

Finding doubles refers to identifying pairs of numbers that sum to a specific value, which is not relevant to skip-counting. Colin's activity does not focus on finding pairs that exceed 55, thereby making this choice unrelated to the counting method described in the question.

Conclusion

Colin's technique of skip-counting by 10s and adding on is the most accurate description of his actions. This method enables him to progress through numbers efficiently while incorporating additional amounts, distinguishing it from decomposition or counting based on unrelated multiples. Understanding this technique is essential for grasping foundational counting strategies in mathematics.

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