Finding the Fourth Proportional to 1,087.89, 1,501.30 and 645.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,087.89 : 1,501.30 = 645.79 : x
2. Step 2: Convert to fraction form
   1,087.89/1,501.30 = 645.79/x
3. Step 3: Cross multiply
   1,087.89x = 1,501.30 × 645.79
4. Step 4: Simplify right side
   1,087.89x = 969,524.53
5. Step 5: Solve for x
   x = 969,524.53/1,087.89
6. Step 6: Final answer
   x = 891.20