Approximate the sum (to the nearest sensible option): 125.009 + 69.999 + 104.989 = ?

Introduction:
Approximation problems reward quick rounding and sensible estimation. Here, the numbers are very close to integers, so rounding each to the nearest whole makes the arithmetic trivial while staying extremely accurate.

Given Data / Assumptions:

• Values: 125.009, 69.999, 104.989
• Goal: Fast approximate sum
• Options are coarse, so nearest-integer rounding suffices

Concept / Approach:
Round each term: 125.009 ≈ 125, 69.999 ≈ 70, 104.989 ≈ 105. Then add. This strategy minimizes error because each term is within about 0.01–0.011 of its rounded integer.

Step-by-Step Solution:

Verification / Alternative check:
Exact sum = 299.997, which rounds to 300. The rounding error is only −0.003, negligible relative to options spacing.

Why Other Options Are Wrong:
285 and 310 are too far from the exact 299.997. 415 and 420 are way off the feasible range of around 300.

Common Pitfalls:
Overcomplicating by keeping all decimals in mental math, or mis-rounding 69.999 down to 69 instead of up to 70.

Final Answer:
300