Ambidextrous means the ability to use right and left hands equally
Total student = right-handed + left-handed students
Let the number of right-handed students = r
Let the number of left-handed students = l
Target question => What percentage of the 20 students in Mr. Henderson's class are left-handed?
What % of the total is l
Total students = boys + girls
Statement 1 => of the 12 girls in the class, 25% are left-handed
Total students = 20, girls = 12; boys = total - girls
Boys = 20 -12 = 8
25% of girls are left-handed
Total left-handed students = left-handed boys + left-handed girls
= (25% of 12) + left-handed boys
Total number of percentage of left-handed boys is unknown. Target question cannot be answered so statement 1 is NOT SUFFICIENT
Statement 2 => 5 of the boys in the class are right-handed
Left-handed boys = total number of boys - 5
Total left-handed boys are unknown, total left-handed girls are also unknown. The available information is not enough to answer the target question. Statement 2 is NOT SUFFICIENT
Combining both statements together =>
From statement 1 => total girls = 12
Total boys = 8
Left-handed girls = 25% of 12 = 3
From statement 2 => right-handed boys = 5
Left-handed boys = 8 - 5 = 3
Total left-handed students = Left-handed boys + left-handed girls
= 3 + 3 = 6
% of left-handed students out of total student = 60/20 * 100/1 = 30%
Combining both statements together ARE SUFFICIENT
Answer = C