Finding the Fourth Proportional to 1,087.60, 1,500.78 and 645.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,087.60 : 1,500.78 = 645.42 : x
2. Step 2: Convert to fraction form
   1,087.60/1,500.78 = 645.42/x
3. Step 3: Cross multiply
   1,087.60x = 1,500.78 × 645.42
4. Step 4: Simplify right side
   1,087.60x = 968,633.43
5. Step 5: Solve for x
   x = 968,633.43/1,087.60
6. Step 6: Final answer
   x = 890.62