Finding the Fourth Proportional to 128.34, 177.30 and 100.71

Step by Step Solution

1. Step 1: Write the proportion equation
   128.34 : 177.30 = 100.71 : x
2. Step 2: Convert to fraction form
   128.34/177.30 = 100.71/x
3. Step 3: Cross multiply
   128.34x = 177.30 × 100.71
4. Step 4: Simplify right side
   128.34x = 17,855.88
5. Step 5: Solve for x
   x = 17,855.88/128.34
6. Step 6: Final answer
   x = 139.13