Finding the Fourth Proportional to 1,091.30, 1,638.15 and 1,020.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,091.30 : 1,638.15 = 1,020.80 : x
2. Step 2: Convert to fraction form
   1,091.30/1,638.15 = 1,020.80/x
3. Step 3: Cross multiply
   1,091.30x = 1,638.15 × 1,020.80
4. Step 4: Simplify right side
   1,091.30x = 1,672,223.52
5. Step 5: Solve for x
   x = 1,672,223.52/1,091.30
6. Step 6: Final answer
   x = 1,532.32