Finding the Fourth Proportional to 1,072.72, 1,610.40 and 640.24

Step by Step Solution

1. Step 1: Write the proportion equation
   1,072.72 : 1,610.40 = 640.24 : x
2. Step 2: Convert to fraction form
   1,072.72/1,610.40 = 640.24/x
3. Step 3: Cross multiply
   1,072.72x = 1,610.40 × 640.24
4. Step 4: Simplify right side
   1,072.72x = 1,031,042.50
5. Step 5: Solve for x
   x = 1,031,042.50/1,072.72
6. Step 6: Final answer
   x = 961.15