Finding the Fourth Proportional to 1,538.78, 2,123.52 and 840.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,538.78 : 2,123.52 = 840.20 : x
2. Step 2: Convert to fraction form
   1,538.78/2,123.52 = 840.20/x
3. Step 3: Cross multiply
   1,538.78x = 2,123.52 × 840.20
4. Step 4: Simplify right side
   1,538.78x = 1,784,181.50
5. Step 5: Solve for x
   x = 1,784,181.50/1,538.78
6. Step 6: Final answer
   x = 1,159.48