Finding the Fourth Proportional to 1,140.38, 1,573.78 and 643.18

Step by Step Solution

1. Step 1: Write the proportion equation
   1,140.38 : 1,573.78 = 643.18 : x
2. Step 2: Convert to fraction form
   1,140.38/1,573.78 = 643.18/x
3. Step 3: Cross multiply
   1,140.38x = 1,573.78 × 643.18
4. Step 4: Simplify right side
   1,140.38x = 1,012,223.82
5. Step 5: Solve for x
   x = 1,012,223.82/1,140.38
6. Step 6: Final answer
   x = 887.62