Finding the Fourth Proportional to 1,087.98, 1,500.72 and 645.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,087.98 : 1,500.72 = 645.57 : x
2. Step 2: Convert to fraction form
   1,087.98/1,500.72 = 645.57/x
3. Step 3: Cross multiply
   1,087.98x = 1,500.72 × 645.57
4. Step 4: Simplify right side
   1,087.98x = 968,819.81
5. Step 5: Solve for x
   x = 968,819.81/1,087.98
6. Step 6: Final answer
   x = 890.48