Mathematics

From a class of girls and boys the probability that one student chosen at random to answer a question will be a girl is 1/3 . If four boys leave the class , the probability that a student chosen at random to answer a question will be a girl is 2/5 . How many boys and girls are there in the class before the four boys leave ?


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ckellesai

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let the no. of girls be x and boys be y...... x/y=1/3 =>3x=y            ...............(I) now 4 boys leave the class is then x/y-4=2/5 =>5x=2y-8 (I)=>5x=2(3x)-8 x=8 now 3x=y =>y=24 therefore no. of girls is 8 and the no. of boy is 24.............. I have tried my best.....hope i helped............

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