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 x₁, x₂, x₃, x₄, x₅ denote the marks in five examinations.
Then `("x"_1+"x"_2+"x"_3+"x"_4+"x"_5)/5≥90`

∴ `(87+92+94+95+"x"_5)/5≥90`

∴ 368 + x₅ ≥ 450
Subtracting 368 from both sides, we get
x₅ ≥ 82
Sunita must obtain minimum 82 marks in 5^th examination to get grade A.