Finding the Fourth Proportional to 1,686.99, 2,327.91 and 978.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,686.99 : 2,327.91 = 978.89 : x
2. Step 2: Convert to fraction form
   1,686.99/2,327.91 = 978.89/x
3. Step 3: Cross multiply
   1,686.99x = 2,327.91 × 978.89
4. Step 4: Simplify right side
   1,686.99x = 2,278,752.51
5. Step 5: Solve for x
   x = 2,278,752.51/1,686.99
6. Step 6: Final answer
   x = 1,350.78