Finding the Fourth Proportional to 1,239.57, 1,710.42 and 715.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,239.57 : 1,710.42 = 715.50 : x
2. Step 2: Convert to fraction form
   1,239.57/1,710.42 = 715.50/x
3. Step 3: Cross multiply
   1,239.57x = 1,710.42 × 715.50
4. Step 4: Simplify right side
   1,239.57x = 1,223,802.83
5. Step 5: Solve for x
   x = 1,223,802.83/1,239.57
6. Step 6: Final answer
   x = 987.28