Select the correct answer to the following equation: [math: 10+20+30=?][Fill in the blank]

Question

BlackTom AI · Accepted Answer

Add the tens directly: 10 + 20 + 30 can be grouped and simplified using place value and the associative/commutative properties of addition.

1) Relevant concepts
- Place value: 10, 20, 30 are multiples of ten (1·10, 2·10, 3·10).
- Commutative property: order of addition does not matter.
- Associative property: grouping of terms does not change the sum.

2) Step-by-step reasoning and intermediate calculations
- Write each term as a multiple of 10: 10 = 1 × 10, 20 = 2 × 10, 30 = 3 × 10.
- Combine the coefficients: (1 × 10) + (2 × 10) + (3 × 10) = (1 + 2 + 3) × 10.
- Compute the sum of coefficients: 1 + 2 + 3 = 6.
- Multiply back by 10: 6 × 10 = 60.

Alternatively, add pairwise:
- 10 + 20 = 30.
- Then 30 + 30 = 60.

3) Why the correct answer is correct
Both approaches show the sum equals 60 by directly combining the tens or by stepwise addition. The place-value method confirms there are six tens in total, giving sixty.

4) Why the other options are incorrect
- a. 50: would be 10 + 20 + 20 or 10 + 40, not equal to the given terms.
- c. 70: would require an extra 10 compared to the actual total.
- d. 80: is too large by 20 (would correspond to 10 + 30 + 40, for example).

Conclusion: The correct choice is b. 60, which matches the provided answer.

Select the correct answer to the following equation: [math: 10+20+30=?][Fill in the blank]单项选择题

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