The 2nd piece is 1 unit. The 1st piece is 4 units (4 times the 2nd). The 3rd piece is 1 unit + 120 cm. The whole wire is 840 cm.<br><br>[[model:questions/solutions/q8360.png]]<br><br>• 1 + 4 + 1 = 6 units, plus 120 → 840 cm<br>• 6 units → 840 − 120 = 720 cm<br>• 1 unit (2nd) → 720 ÷ 6 = 120 cm<br>• Longest = 1st = 4 units → 4 × 120 = 480 cm<br><br>The longest piece is 480 cm.<br>Check: 2nd 120 + 1st 480 + 3rd 240 = 840 cm. ✓