Finding the Fourth Proportional to 1,087.84, 1,501.20 and 645.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,087.84 : 1,501.20 = 645.89 : x
2. Step 2: Convert to fraction form
   1,087.84/1,501.20 = 645.89/x
3. Step 3: Cross multiply
   1,087.84x = 1,501.20 × 645.89
4. Step 4: Simplify right side
   1,087.84x = 969,610.07
5. Step 5: Solve for x
   x = 969,610.07/1,087.84
6. Step 6: Final answer
   x = 891.32