Finding the Fourth Proportional to 12,816.96, 17,688.62 and 7,780.02

Step by Step Solution

1. Step 1: Write the proportion equation
   12,816.96 : 17,688.62 = 7,780.02 : x
2. Step 2: Convert to fraction form
   12,816.96/17,688.62 = 7,780.02/x
3. Step 3: Cross multiply
   12,816.96x = 17,688.62 × 7,780.02
4. Step 4: Simplify right side
   12,816.96x = 137,617,817.37
5. Step 5: Solve for x
   x = 137,617,817.37/12,816.96
6. Step 6: Final answer
   x = 10,737.17