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The ratio of number of boys and girls in a class is 3 : 2. In the 1st semester exam 20% of boys and 25% of girls get more than or equal to 90% marks. What percentage of students get less than 90% marks ?

The ratio of number of boys and girls in a class is 3 : 2.  In the 1st semester exam 20% of boys and 25%
    of girls get more than or equal to 90%  marks. What percentage of students get less than 90% marks ?

a) 56    b) 70    c) 78    d) 80











. Expl : Let boys =3x and girls =2x.

    Number of those who get less than 90% mark  =(80% of 3x) + (75% of 2x)

    =(80/100 )*3x +(75/100 *2x)  =39x/10

    Required percentage = (39x/10 *1/5x *100)% = 78%.
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