50 students preferred science...
Explanation:
we can consider the numbers 5 and 4 in the ratio as units
now we need to know how much each unit represent
units = 5 + 4 = 9
my sample = 90 students
each unit = 90/9 = 10 students
so each unit represents 10 students
back to the ratio
who preferred science = 5
who preferred English = 4
Number of students choose Science = 5 * 10 = 50
