What is the opening price if limit orders on both sides are on equal order size?

• A. Arithmetical mean of the prices of the two last-executed orders
• B. Price of the last-executed order
• C. Maximum executable trading volume
• D. Reference price

Answer: (A)

When determining the opening price in an opening auction, the market looks for a price that clears the maximum volume given the orders on both sides. If the limit orders on the buy and sell sides are equal in size, there is a perfectly balanced cross, so the price that clears is halfway between the two most recent executable trades—i.e., the arithmetic mean of the prices of the two last-executed orders. This choice avoids bias toward either side and reflects a fair midpoint when supply and demand are matched equally. The other options don’t fit: taking the price of just the last trade would tilt one way or the other, the maximum executable volume is a quantity, and a reference price is a separate benchmark not used to set the opening cross in this balanced case.