Finding the Fourth Proportional to 1,686.90, 2,327.86 and 978.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,686.90 : 2,327.86 = 978.76 : x
2. Step 2: Convert to fraction form
   1,686.90/2,327.86 = 978.76/x
3. Step 3: Cross multiply
   1,686.90x = 2,327.86 × 978.76
4. Step 4: Simplify right side
   1,686.90x = 2,278,399.72
5. Step 5: Solve for x
   x = 2,278,399.72/1,686.90
6. Step 6: Final answer
   x = 1,350.64