In a class, there are 54 students. 33 $$\frac{1}{3}$$ % of the number of students are boys and rest are girls. The average score in mathematics of boys is 50% more than that of the girls. If the average score of all the students is 70, then what is the average score of the boys?

Number of student in class = 54 

number of boys = $$33\dfrac {1}{3}of student = \dfrac{100}{3\times 100} \times 54 = 18$$

then number of girls = 54-18 = 36 

Let Average score of girls =$$ 10x$$

and average score of boys =$$ \dfrac {10x \times150}{100} = 15x $$(according to question)   

average score of all student =  70 

total score of  54 = $$54 \times70 $$ =3780 

total score of boys = $$18\times 15x = 270x $$

total score of girls =$$36\times10x = 360x  $$

according question $$ 270x +360x =3780$$

$$\Rightarrow x = 6 $$

Average score boy = $$15\times$$ = 90 Ans.