Finding the Fourth Proportional to 1,087.27, 1,500.78 and 645.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,087.27 : 1,500.78 = 645.31 : x
2. Step 2: Convert to fraction form
   1,087.27/1,500.78 = 645.31/x
3. Step 3: Cross multiply
   1,087.27x = 1,500.78 × 645.31
4. Step 4: Simplify right side
   1,087.27x = 968,468.34
5. Step 5: Solve for x
   x = 968,468.34/1,087.27
6. Step 6: Final answer
   x = 890.73