Finding the Fourth Proportional to 1,215.34, 1,677.15 and 717.91

Step by Step Solution

1. Step 1: Write the proportion equation
   1,215.34 : 1,677.15 = 717.91 : x
2. Step 2: Convert to fraction form
   1,215.34/1,677.15 = 717.91/x
3. Step 3: Cross multiply
   1,215.34x = 1,677.15 × 717.91
4. Step 4: Simplify right side
   1,215.34x = 1,204,042.76
5. Step 5: Solve for x
   x = 1,204,042.76/1,215.34
6. Step 6: Final answer
   x = 990.70