Linear Inequalities

The marks obtained by a student in two tests were 70 and 75. Find the number of minimum marks he should get in the third test to have an average of at least 60 marks. [NCERT]

The longest side of a triangle is three times the shortest side and third side is 2 cm shorter than the longest side. If the perimeter of triangle is at least 61 cm. Find the minimum length of the shortest side.

A solution of 8% basic acid is to be diluted by adding 2% boric solution to it. The resulting mixture is to be more than 4% but less than 6% basic acid. If we have 640 litres of the 8% solution, how many litres of the 2% solution will have to be added.

A plumber can be paid under two schemes as given below :
Scheme I : Rs. 600 and Rs. 50 per hour.
Scheme II: Rs. 170 per hour.
If the job takes x hours, for what values of x does the scheme I give the plumber the better wages ?

A manufacturer has 600 litres of a 12% solution of acid. How many litres of a 30% acid solution must be added to it so that acid content in the resulting mixture will be more than 15% but less than 18% ?

Solve forx : |x| <4.