Finding the Fourth Proportional to 128.46, 177.10 and 100.72

Step by Step Solution

1. Step 1: Write the proportion equation
   128.46 : 177.10 = 100.72 : x
2. Step 2: Convert to fraction form
   128.46/177.10 = 100.72/x
3. Step 3: Cross multiply
   128.46x = 177.10 × 100.72
4. Step 4: Simplify right side
   128.46x = 17,837.51
5. Step 5: Solve for x
   x = 17,837.51/128.46
6. Step 6: Final answer
   x = 138.86