# A student scored 75, 85, and 93 on three algebra tests. What must he score on the fourth test in order to have an average grade of at least 85?

Oct 24, 2016

$87$

#### Explanation:

Let the score of the fourth test be $= x$,

$\implies \frac{75 + 85 + 93 + x}{4} = 85$

$\implies 253 + x = 85 \times 4$
$\implies x = 340 - 253 = 87$

Hence, the student must score at least 87 marks on the fourth test.

Oct 24, 2016

87 or more

#### Explanation:

$\frac{75 + 85 + 93 + x}{4} \ge 85$

$\frac{253 + x}{4} \cdot 4 \ge 85 \cdot 4$

$253 + x \ge 340$

$x \ge 340 - 253$

$x \ge 87$