Finding the Fourth Proportional to 128,431.72, 177,242.66 and 71,839.72

Step by Step Solution

1. Step 1: Write the proportion equation
   128,431.72 : 177,242.66 = 71,839.72 : x
2. Step 2: Convert to fraction form
   128,431.72/177,242.66 = 71,839.72/x
3. Step 3: Cross multiply
   128,431.72x = 177,242.66 × 71,839.72
4. Step 4: Simplify right side
   128,431.72x = 12,733,063,066.46
5. Step 5: Solve for x
   x = 12,733,063,066.46/128,431.72
6. Step 6: Final answer
   x = 99,142.67