Finding the Fourth Proportional to 1,388.53, 2,081.76 and 840.58

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.53 : 2,081.76 = 840.58 : x
2. Step 2: Convert to fraction form
   1,388.53/2,081.76 = 840.58/x
3. Step 3: Cross multiply
   1,388.53x = 2,081.76 × 840.58
4. Step 4: Simplify right side
   1,388.53x = 1,749,888.42
5. Step 5: Solve for x
   x = 1,749,888.42/1,388.53
6. Step 6: Final answer
   x = 1,260.25