In an examination, 1100 boys and 900 girls appeared, 50% of the boys and 40% of the girls passed the examination. The percentage of candidates who failed :

Total number boy = 1100 and girl = 900
Total number of boy fail (50%) = 550
Total number of girl fail ( 60%) = 540
Total failed candidates = (550 + 540) = 1090
Required percentage of failed candidates :
= $$\frac{1090}{(1100 + 900)}$$   × 100
= $$\frac{1080 × 100}{2000}$$
= 54.5%