Failed = 25% = 1 unit; passed = 75% = 3 units, so the whole class is 4 units. The 16 extra pupils make up 2 units.<br><br>[[model:questions/solutions/q5447.png]]<br><br>• Passed − failed → 2 units → 16<br>• 1 unit → 16 ÷ 2 = 8<br>• Whole class → 4 units = 4 × 8 = 32<br><br>There are 32 pupils in the class.<br>Check: failed 8 + passed 24 = 32; 8 is 25% of 32. ✓