Finding the Fourth Proportional to 42,728.96, 64,069.94 and 13,138.58

Step by Step Solution

1. Step 1: Write the proportion equation
   42,728.96 : 64,069.94 = 13,138.58 : x
2. Step 2: Convert to fraction form
   42,728.96/64,069.94 = 13,138.58/x
3. Step 3: Cross multiply
   42,728.96x = 64,069.94 × 13,138.58
4. Step 4: Simplify right side
   42,728.96x = 841,787,744.78
5. Step 5: Solve for x
   x = 841,787,744.78/42,728.96
6. Step 6: Final answer
   x = 19,700.64