Question 765446
Ratio of boys to girls = 5:1

Assume that the number of girls is x

If there are x girls in the class there are 5*x boys 

Total number of students = 6*x

Average score for the whole class of 6*x students = p.

So total marks scored by the class = {{{6*x*p}}}
(Remember that average for all students = total / number of students)

Similarly, Average score of boys = p+1

So total marks scored by boys = {{{5*x*(p+1) = 5*x*p + 5*x}}}

So, total marks scored only by girls = {{{6*x*p - 5*x*p - 5*x = x*p - 5*x = x*(p - 5)}}}

Since there are x girls, average score for the girls = total score for girls / number of girls

= {{{x*(p - 5)/x = p - 5}}}

Hope you got it :)

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