Finding the Fourth Proportional to 71.93, 107.72 and 71.31

Step by Step Solution

1. Step 1: Write the proportion equation
   71.93 : 107.72 = 71.31 : x
2. Step 2: Convert to fraction form
   71.93/107.72 = 71.31/x
3. Step 3: Cross multiply
   71.93x = 107.72 × 71.31
4. Step 4: Simplify right side
   71.93x = 7,681.69
5. Step 5: Solve for x
   x = 7,681.69/71.93
6. Step 6: Final answer
   x = 106.80