Why Students Fail in MATHS EXAM ?

In a class, 15% of total number of students failed in Science, 25% of total number of students failed in Maths and 10% of total number of students failed in both. How much percentage of students passed in both Maths and Science?

In an examination, 35% students failed in Hindi, 45% students failed in English and 20% students failed in both the subjects. What is the percentage of students passing in both the subjects?

In an examination, 49% students failed in English, 36% students failed in Hindi, while 15% failed in both. If total number of passed students is 450, then how many students did appear in the examination?