Question

To receive Grade ‘A’ in a course, one must obtain an average of 90 marks or more in five examinations (each of 100 marks). If Sunita’s marks in first four examinations are 87, 92, 94 and 95, find minimum marks that Sunita must obtain in fifth examination to get grade ‘A’ in the course.

Answer 1

Let x be the marks obtained by Sunita in the fifth examination.

Average of marks obtained in five exams = `(87  +  92 +  94  +  95  + x)/5  ≥ 90`

= `(368  + x)/5`

According to Question,

∴ `(368  +  x)/5  ≥ 90`

Multiplying both sides by 5

368 + x ≥ 5 x 90

or 368 + x ≥ 450

or x ≥ 450 – 368

∴ x ≥ 82

Thus, Sunita must obtain greater than or equal to 82 marks in the fifth examination.