Question

Every student of a class gets either of the grades A, B, C, D or E. 20% students of a class got grade A and 25% of the rest got grade B. If 15% of them got grade C, ratio and difference of students securing grades D and E are 4 : 5 and 5 respectively, then the number of students securing grades E and C respectively are

Answer 1

Number of students who got grade A = 20%

Number of students who got grade B = 25% of the remaining = 25% of 80% = 0.25*0.8 = 0.2 = 20%.

Number of students who got grade C = 15%.

Therefore, total of students who got grade D and E is 100% - (20%+20%+15%) = 45%.

Ratio of students who got grade D and E is 4:5

$\frac{0.45}{9}=0.05=5$%

Therefore, the number of students who got grade D is 20% and the number of students who got grade E is 25%.

Since the difference of students who got grade D and E is 5, therefore, each student resembles 1% of the total.

Therefore, the number of students who got grade E is 25, and the number of students who got grade C is 15.