There were an equal number of girls in Class C and Class D. ⁴₅ of the students in Class C and ¹₆ of the students in Class D are boys. If there are 152 more boys in Class C than in Class D, what is the total number of students in Class C and Class D?
Fraction of the students in Class C that are girls
= 1 - ⁴₅
=  ¹₅

Fraction of the students in Class D that are girls
= 1 - ¹₆
= ⁵₆ 

The number of girls in Class C is equal to the number of girls in Class D. LCM of 1 and 5 is 5. Make the numerators the same. 

 1x55x5 Class C = 56 Class D 
 525 Class C = 56 Class D

Number of girls in each class = 5 u

Total number of students in Class C = 25 u
Total number of students in Class D = 6 u

Number of boys in Class C
= 25 u - 5 u
= 20 u

Number of boys in Class D
= 6 u - 5 u
= 1 u

Number of more boys in Class C than Class D
= 20 u - 1 u
= 19 u

19 u = 152

1 u = 152 ÷ 19 = 8

Total number of students
= 25 u + 6 u
= 31 u
= 31 x 8
= 248

Answer(s): 248