Bacaan
Protect the Lane, and They Will Ride? (fictional report)
KOTA LARASATI (fictional) — In October 2025, the city council of Kota Larasati replaced the painted bicycle lane on Jalan Melati with a lane separated from traffic by a low concrete kerb. To see what changed, council staff counted the traffic passing one point on the street between 06.00 and 09.00 on five weekday mornings in September 2025, before the work began, and again on five weekday mornings in March 2026. The table shows the average count per morning.
| Road user | September 2025 | March 2026 |
|---|---|---|
| Bicycles | 180 | 420 |
| Motorcycles | 2,400 | 2,150 |
| Cars | 900 | 880 |
In March, the staff also interviewed 150 cyclists on Jalan Melati who said they had not cycled on the street before the new lane opened. Of these, 84 said they used to make the same trip by motorcycle, 39 by shared minibus (angkot), and 27 by car.
"The numbers speak for themselves," said council member Dewi Anggraini (fictional). "Protect the lane, and people will ride. We should build the same kind of lane on every major street in the city."
Soal 1
Pilih satu jawabanBy about what percentage did the average number of motorcycles counted per morning fall between September 2025 and March 2026?
Lihat kunci & pembahasan
Kunci: B
Kenapa benar
Jumlah sepeda motor turun 2.400 − 2.150 = 250. Persentase penurunan dihitung terhadap nilai awal: 250 ÷ 2.400 ≈ 0,104, yaitu sekitar 10%.
Langkah
Diketahui: sepeda motor September 2025 = 2.400, Maret 2026 = 2.150.
Ditanya: persentase penurunan.
Metode: persentase perubahan = selisih ÷ nilai awal × 100%.
Hitung: selisih = 250; 250 ÷ 2.400 × 100% ≈ 10,4%, dibulatkan sekitar 10%.
Cek: 10% dari 2.400 = 240, dekat dengan 250. Masuk akal.
Tips: pembagi persentase perubahan selalu nilai awal (sebelum perubahan).
Kenapa opsi lain salah
- A.
Angka 7% muncul bila 250 dibagi total semua kendaraan bulan September (3.480). Pertanyaan meminta penurunan sepeda motor terhadap jumlah sepeda motor sendiri.
- C.
Angka 12% muncul bila 250 dibagi nilai akhir (2.150 → 11,6%). Pembagi yang benar adalah nilai awal 2.400.
- D.
Angka 90% adalah perbandingan 2.150 ÷ 2.400 (≈ 89,6%), yaitu jumlah yang tersisa, bukan besar penurunannya.
- E.
Angka 133% adalah kenaikan jumlah sepeda (240 ÷ 180), bukan perubahan jumlah sepeda motor. Kemungkinan baris tabel tertukar.
Konsep
Persentase perubahan dihitung sebagai selisih dibagi nilai awal; nilai akhir dibagi nilai awal menghasilkan proporsi yang tersisa, bukan perubahan.
Jebakan umum
Membagi selisih dengan nilai akhir.
Membaca baris tabel yang salah (sepeda, bukan sepeda motor).
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