Finding the Fourth Proportional to 42.18, 63.30 and 20.82

Step by Step Solution

1. Step 1: Write the proportion equation
   42.18 : 63.30 = 20.82 : x
2. Step 2: Convert to fraction form
   42.18/63.30 = 20.82/x
3. Step 3: Cross multiply
   42.18x = 63.30 × 20.82
4. Step 4: Simplify right side
   42.18x = 1,317.91
5. Step 5: Solve for x
   x = 1,317.91/42.18
6. Step 6: Final answer
   x = 31.24