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 ?  Choose the correct choice:
A) 56	B) 70	C) 78	D) 80	E) 85
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%.   ANSWER:78(39 /10 *1/5  *100)= 
<gadget id="calculator">(39 /10 *1/5  *100)</gadget>
<output>78</output>
78%.   ANSWER:78
<result>C</result>
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 ?