Finding the Fourth Proportional to 1,140.86, 1,574.25 and 643.47

Step by Step Solution

1. Step 1: Write the proportion equation
   1,140.86 : 1,574.25 = 643.47 : x
2. Step 2: Convert to fraction form
   1,140.86/1,574.25 = 643.47/x
3. Step 3: Cross multiply
   1,140.86x = 1,574.25 × 643.47
4. Step 4: Simplify right side
   1,140.86x = 1,012,974.33
5. Step 5: Solve for x
   x = 1,012,974.33/1,140.86
6. Step 6: Final answer
   x = 887.91