Finding the Fourth Proportional to 1,072.72, 1,609.20 and 781.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,072.72 : 1,609.20 = 781.12 : x
2. Step 2: Convert to fraction form
   1,072.72/1,609.20 = 781.12/x
3. Step 3: Cross multiply
   1,072.72x = 1,609.20 × 781.12
4. Step 4: Simplify right side
   1,072.72x = 1,256,978.30
5. Step 5: Solve for x
   x = 1,256,978.30/1,072.72
6. Step 6: Final answer
   x = 1,171.77