Finding the Fourth Proportional to 12,420, 17,139.60 and 7,116.53

Step by Step Solution

1. Step 1: Write the proportion equation
   12,420 : 17,139.60 = 7,116.53 : x
2. Step 2: Convert to fraction form
   12,420/17,139.60 = 7,116.53/x
3. Step 3: Cross multiply
   12,420x = 17,139.60 × 7,116.53
4. Step 4: Simplify right side
   12,420x = 121,974,391.89
5. Step 5: Solve for x
   x = 121,974,391.89/12,420
6. Step 6: Final answer
   x = 9,820.80