IPA FE Subject A 2025 Question 7
A question IPA Japan published in 令和７年度 基本情報技術者試験 科目A 公開問題 問7, translated into English. ITPEC is based on the same exams.
When 1 Gbyte of video data was downloaded using a 40 Mbit/s line, it took 5 minutes. Approximately what is the line utilization rate in percentage in this case? Here, during the download, control information of 20% is added to the video data.
Explanation
80% — compare the bits actually sent, control information included, with what the line could carry in 5 minutes.
- •Data sent: 1 Gbyte × 1.2 = 1.2 Gbytes = 1.2 × 8 = 9.6 Gbits
- •Line capacity in 5 minutes: 40 Mbit/s × 300 s = 12,000 Mbits = 12 Gbits
- •Utilization rate: 9.6 ÷ 12 = 0.8, that is, 80%
Answer (d)
Why not others:
- •(a) 10 — forgets to convert bytes to bits: 1.2 ÷ 12 = 0.1
- •(b) 53 — takes the 20% off the data instead of adding it: 0.8 × 8 = 6.4 Gbits, 6.4 ÷ 12 ≈ 0.53
- •(c) 67 — leaves out the control information: 8 ÷ 12 ≈ 0.67
Key rule: Line utilization rate = bits actually transmitted (data plus control information, bytes × 8) ÷ (line speed × time).
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This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.