The cost price of 10 pens is the same as the selling price of n pens. If there is a loss of 40%, approximately what is the value of n?

Solve the following problems:

A triangular plot with sides of 25 feet, 40 feet and 55 feet is to surround by a fence built on pillars set 5 feet apart. How many pillars will be required to surround the plot?

Solve the following problems:

In a class of 78 students 41 are taking French, 22 are taking German. Of the students taking French or German, 9 are taking both courses. How many students are not enrolled in either courses?

Solve the following problems:

The average age of 12 children is 15 years. If another child comes the average age comes to 14. What is the age of the new child?

Solve the following problems:

$find the value of n, if {27}^{-\frac{1}{3^n}}=243$

Solve the following problems:

if 16+4x is 10 more than 14, what is the value of 8x?