Question

In examination, ${\text{42% }}$students failed in mathematics and ${\text{52% }}$failed in science. If ${\text{17% }}$failed in both the subjects. Find the percentage who passed in both the subjects?

Hint: First let us calculate individual failing of the students in both the subjects from there we can use the logic that
${\text{ = 100% - (fail% )}}$, and on using above equation we can obtain our required answer.

As given that ${\text{17% }}$failed in both the subjects, and ${\text{42% }}$students failed in mathematics and ${\text{52% }}$failed in science.
The number of students that only failed in mathematics${\text{ = 42 - 17 = 25% }}$
The number of students that only failed in science${\text{ = 52 - 17 = 35% }}$
${\text{ = 35 + 25 + 17% }} \\ {\text{ = 77% }} \\$
${\text{ = 100% - (fail% )}} \\ {\text{ = 100 - (77)% }} \\ {\text{ = 23% }} \\$