Finding the Fourth Proportional to 12,840.48, 17,721.90 and 7,806.28

Step by Step Solution

1. Step 1: Write the proportion equation
   12,840.48 : 17,721.90 = 7,806.28 : x
2. Step 2: Convert to fraction form
   12,840.48/17,721.90 = 7,806.28/x
3. Step 3: Cross multiply
   12,840.48x = 17,721.90 × 7,806.28
4. Step 4: Simplify right side
   12,840.48x = 138,341,985.89
5. Step 5: Solve for x
   x = 138,341,985.89/12,840.48
6. Step 6: Final answer
   x = 10,773.90