Finding the Fourth Proportional to 1,538.79, 2,123.55 and 840.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,538.79 : 2,123.55 = 840.21 : x
2. Step 2: Convert to fraction form
   1,538.79/2,123.55 = 840.21/x
3. Step 3: Cross multiply
   1,538.79x = 2,123.55 × 840.21
4. Step 4: Simplify right side
   1,538.79x = 1,784,227.95
5. Step 5: Solve for x
   x = 1,784,227.95/1,538.79
6. Step 6: Final answer
   x = 1,159.50