Sunita has scored $87, 92, 94, 95$ in four exams (each out of $100$). To earn Grade A she needs an average of at least $90$ across **five** exams. What is the minimum mark she must obtain in the fifth exam?

Let $x$ be the fifth-exam mark. $\dfrac{87 + 92 + 94 + 95 + x}{5} \geq 90 \Rightarrow \dfrac{368 + x}{5} \geq 90 \Rightarrow 368 + x \geq 450 \Rightarrow x \geq 82$. Minimum mark: **82** (and feasible since $82 \leq 100$).