Step 1: Calculate Sale Value of Machinery Sold
Cost of machinery sold = Rs. 1,40,000
Less: Accumulated Depreciation = Rs. 90,000
$\Rightarrow$ Book Value = Rs. 50,000
Gain on sale = Rs. 10,000
$\Rightarrow$ Sale Price = Rs. 50,000 + Rs. 10,000 = Rs. 60,000
Step 2: Calculate Purchase of Machinery
Let machinery purchased = Rs. $x$
Opening Gross Block = Rs. 50,00,000
Less: Cost of machinery sold = Rs. 1,40,000
Add: Purchases = $x$
Closing Gross Block = Rs. 70,00,000
$70,00,000 = 50,00,000 - 1,40,000 + x \Rightarrow x = 21,40,000$
Step 3: Calculate Cash Flow from Investing Activities
Outflow: Purchase of Machinery = Rs. 21,40,000
Inflow: Sale of Machinery = Rs. 60,000
$\textbf{Net Cash Used in Investing Activities} = 21,40,000 - 60,000 = Rs. 20,80,000$
Final Answer:
$\boxed{\text{Cash Used in Investing Activities} = \text{Rs. } 20,80,000}$