Finding the Fourth Proportional to 111.91, 167.58 and 71.21

Step by Step Solution

1. Step 1: Write the proportion equation
   111.91 : 167.58 = 71.21 : x
2. Step 2: Convert to fraction form
   111.91/167.58 = 71.21/x
3. Step 3: Cross multiply
   111.91x = 167.58 × 71.21
4. Step 4: Simplify right side
   111.91x = 11,933.37
5. Step 5: Solve for x
   x = 11,933.37/111.91
6. Step 6: Final answer
   x = 106.63