In one hour there are 3600 seconds. What decimal part of an hour is represented by a single second? Give the answer correct to five decimal places.

Introduction / Context:
This question connects time measurement with decimal fractions. It asks you to express one second as a decimal part of an hour, which is common in speed, work, and time calculations where hours are used as the main unit and smaller time units must be converted accurately.

Given Data / Assumptions:

• 1 hour = 60 minutes.
• 1 minute = 60 seconds.
• Therefore, 1 hour = 60 × 60 = 3600 seconds.
• We wish to express 1 second as a fraction, and then as a decimal, of 1 hour.
• The answer choices are in decimal form and are close in value, so attention to place value and rounding is important.

Concept / Approach:
We interpret the phrase "what decimal of an hour" as the ratio (time in seconds) / (3600 seconds). Since we want the decimal for one second, we compute 1 divided by 3600. The resulting value is then rounded to the required number of decimal places to match the pattern of the options. This type of ratio-to-decimal conversion is standard in decimal fraction problems.

Step-by-Step Solution:
Total seconds in one hour = 60 × 60 = 3600 seconds.We want the fraction of an hour represented by 1 second: this is 1 / 3600.Compute 1 / 3600 as a decimal: 1 ÷ 3600 ≈ 0.0002777777...To match the style of the options, round this to five decimal places.0.0002777777... rounds to 0.00028 (since the sixth decimal digit is 7, which causes rounding up).Therefore, one second is approximately 0.00028 of an hour.

Verification / Alternative check:
We can reverse check by multiplying 0.00028 by 3600. Compute 0.00028 × 3600 = 1.008. This is very close to 1 second, with the small difference due to rounding. If we used more decimal places, the product would be even closer to exactly 1. This confirms that 0.00028 is a valid rounded representation of one second as a decimal part of an hour.

Why Other Options Are Wrong:
Option 0.00027 is slightly smaller and would give 0.972 seconds when multiplied by 3600, which underestimates a second. Option 0.00026 and 0.00025 are even smaller and deviate more from the true value 1/3600. Option 0.00030 is larger and would correspond to 1.08 seconds of an hour, which overestimates the actual time. Therefore, only 0.00028 is a reasonable rounded match to 1 / 3600.

Common Pitfalls:
Some learners mistakenly divide 1 by 60 instead of by 3600, effectively computing the fraction of a minute instead of an hour. Others misplace the decimal when dividing by large numbers, producing 0.0028 or similar values that are ten times or one hundred times larger than the correct answer. Remembering that an hour contains 3600 seconds and performing the division carefully avoids these errors.

Final Answer:
One second is approximately 0.00028 of an hour when expressed as a decimal fraction.