Opening Stock:
The opening stock refers to the value of goods or inventory available at the beginning of a specific accounting period. In this case, the opening stock is given as 18,000.

Purchases:
Purchases are the cost of acquiring goods or inventory during a specific accounting period. In this case, the purchases amount is given as 1,20,000.

Wages:
Wages refer to the amount paid to employees for their services. In this case, the wages amount is given as 9,000.

Gross Profit Rate:
The gross profit rate is the percentage of profit earned on sales. In this case, the gross profit rate is given as 20% on sales.

Closing Stock:
The closing stock refers to the value of goods or inventory available at the end of a specific accounting period. In this case, the closing stock is given as 27,000.

Calculation of Sales:
To calculate the sales, we need to find the cost of goods sold (COGS). The formula to calculate COGS is:
COGS = Opening Stock + Purchases + Direct Expenses - Closing Stock

In this case, the direct expenses are not given. Therefore, we can assume that there are no direct expenses. Using the given values, we can calculate the COGS as follows:
COGS = 18,000 + 1,20,000 + 0 - 27,000
COGS = 1,11,000

Now, we can calculate the sales using the formula:
Sales = COGS + Gross Profit

Since the gross profit rate is given as 20%, we can calculate the gross profit as a percentage of sales:
Gross Profit = Gross Profit Rate * Sales
Gross Profit = 0.20 * Sales

Substituting the values, we can rewrite the formula as:
Sales = COGS + 0.20 * Sales

Simplifying the equation, we get:
Sales - 0.20 * Sales = COGS
0.80 * Sales = COGS
Sales = COGS / 0.80

Substituting the value of COGS, we get:
Sales = 1,11,000 / 0.80
Sales = 1,38,750

Therefore, the sales amount is 1,38,750.

Summary:
- Opening Stock: 18,000
- Purchases: 1,20,000
- Wages: 9,000
- Gross Profit Rate: 20% on sales
- Closing Stock: 27,000
- COGS: 1,11,000
- Sales: 1,38,750