$\begin{array}{1 1} (A)\;78 \\(B)\;35 \\(C)\;56 \\(D)\;20 \end{array} $

- Same Quantity can be added (a subtracted ) to (from ) both sides of the inequality with out changing the sign of the in equality.
- Same positive quantities can be multiplied or divided to both side of the in equality with out changing the sign of the inequality.
- If same negative quantity is multiplied or divided to both sides of the inequality is reversed i.e $ '>'$ sign changes to $'<' $ and $'<'$ changes $'>'$ .

Let x be the mark Ravi obtained in the third unit test.

Total marks obtained in the three test is $70+75+x$

Since the average marks of the three test in at least 60 $\large\frac{70 +75+x}{3} $$ \geq 60$

Multiplying both sides of inequality by 3 .

$145 + x \geq 180$

Subtracting 145 from both sides of the inequality.

$x \geq 180-145$

$x \geq 35$

Step 2:

The student must obtain a minimum mark of 35 to get an average of 60 marks.

Hence B is the correct answer.

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