In a class, 65% of the students are boys. On a particular day 80% of girl students were present. What was the fraction of boys who were present that day if the total number of students present that day was 70%?

Let the class has 100 students.

$\Rightarrow$ Number of girls = 35 and number of boys = 65. 

Since total na umber of present students = 70 and number of girls present= 80% of 35 = 28, so number of boys present = 70 -28 = 42. 

$\Rightarrow$ Required fraction = 42/65.