3. Percentage Application

Illustration 9
        In an examination, 96% of the candidates passed & 50 failed. How many candidates appeared ?
    Solution 
        Let the number of candidates appeared be x 
        Percentage of those who passed = 96%
        Percentage of those who failed = (100 – 96)% = 4 %
        Number of failures = 4% of x.
   ∴      4% of x = 50

Hence, the number of candidates appeared is 1250.

    Illustration 10    
        (i)     Chalk contains calcium, carbon and oxygen in the ratio 10 : 3 : 12, find the % of carbon in chalk.
        (ii)     If in a stick of chalk, carbon is 3g, what is the weight of the chalk stick ?