Question

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 ?​

Answer 1

Answer:78%

Step-by-step explanation:

Let no. of boys = 3x

so , no. of girls= 2x

hence , total students = 5x

No. of boys who scored above 90%  = 20/100×3x

                                                             =3x/5

No. of girls who scored above 90% = 25/100×2x

                                                           =x/2

total students who scored above 90%= 3x/5 + x/2

                                                               = 11x/10

now,

percentage of students who scored above 90% =(11x/10) ÷ (5x) × 100

                                                                                = 22%

Hence %age of students who scored less than 90% = 100 - 22

                                                                                       = 78%