Finding the Fourth Proportional to 1,140.56, 1,573.98 and 643.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,140.56 : 1,573.98 = 643.15 : x
2. Step 2: Convert to fraction form
   1,140.56/1,573.98 = 643.15/x
3. Step 3: Cross multiply
   1,140.56x = 1,573.98 × 643.15
4. Step 4: Simplify right side
   1,140.56x = 1,012,305.24
5. Step 5: Solve for x
   x = 1,012,305.24/1,140.56
6. Step 6: Final answer
   x = 887.55