Finding the Fourth Proportional to 1,057.80, 1,580.01 and 840.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,057.80 : 1,580.01 = 840.72 : x
2. Step 2: Convert to fraction form
   1,057.80/1,580.01 = 840.72/x
3. Step 3: Cross multiply
   1,057.80x = 1,580.01 × 840.72
4. Step 4: Simplify right side
   1,057.80x = 1,328,346.01
5. Step 5: Solve for x
   x = 1,328,346.01/1,057.80
6. Step 6: Final answer
   x = 1,255.76