The average cost price of 15 pens (having equal cost price) decreased by Rs.2, when one of the pen is replaced by a new pen having cost price of Rs.70. Find the cost price of the pen that was replaced.
Let the cost price of each pen be Rs.x So, cost price of 15 pens = Rs.15x According to the question, => (15x – x + 70)/15 = x – 2 => 14x + 70 = 15x – 30 => x = 100 Therefore, the cost price of the pen that was replaced is = Rs.100
