Finding the Fourth Proportional to 1,215.86, 1,677.88 and 691.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,215.86 : 1,677.88 = 691.89 : x
2. Step 2: Convert to fraction form
   1,215.86/1,677.88 = 691.89/x
3. Step 3: Cross multiply
   1,215.86x = 1,677.88 × 691.89
4. Step 4: Simplify right side
   1,215.86x = 1,160,896.54
5. Step 5: Solve for x
   x = 1,160,896.54/1,215.86
6. Step 6: Final answer
   x = 954.80