Competition · AMC preparation · step 4 of 4
AMC 8 · 2001 · #1
Grade 4 arithmeticrate-ratioPick an answer.
AMC 8 2001 problem © Mathematical Association of America (MAA AMC). Reproduced for educational use.
The question mixes two ideas: how long the painting takes, and what unit the answer should be in. Tool #7 (Break into Subproblems) splits the work into two clean steps — first find the total time in seconds, then deal with the unit. Tool #16 (Change Representation) handles the second step: rewriting a seconds total as minutes by dividing by 60. Keeping the two steps separate prevents unit-mixing mistakes.
Find the total seconds
Total time in seconds: 300 dimples times 2 seconds each gives 600 seconds.
Grade 4 multiplicative comparison: "300 dimples, 2 seconds each" means total = (count) × (time per item).
4.OA.A.2Identify SubproblemsConvert seconds to minutes
Convert seconds to minutes: divide 600 by 60 to get 10 minutes.
Grade 4 measurement conversion: dividing by 60 regroups seconds into whole minutes.
To express the 600-second painting time in minutes, you divide 600 by 60.
▸ Why?
A minute is always exactly 60 seconds, so each block of 60 painting-seconds is worth one whole minute, and counting those blocks is what "how many minutes" asks for.
▸ Why?
Splitting the 600 seconds into equal 60-second minutes is a division, and dividing by 60 exactly undoes the multiplying-by-60 that would rebuild the seconds from minutes, so it returns the minute count.
Match against the choices
Match the result to the choices: 10 minutes is choice (D).
Reading off the choice that matches the computed value is the last step of a multistep word problem.
4.OA.A.3Identify SubproblemsWhen a problem mixes amounts and units, do them in order: first compute the total in the unit you were given, then convert to the unit the question asks for. Here that means seconds first (300 × 2 = 600), minutes second (600 ÷ 60 = 10).
- Find the total seconds
- Convert seconds to minutes
- Match against the choices
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