Finding the Fourth Proportional to 31.31, 42.61 and 31.18

Step by Step Solution

1. Step 1: Write the proportion equation
   31.31 : 42.61 = 31.18 : x
2. Step 2: Convert to fraction form
   31.31/42.61 = 31.18/x
3. Step 3: Cross multiply
   31.31x = 42.61 × 31.18
4. Step 4: Simplify right side
   31.31x = 1,328.58
5. Step 5: Solve for x
   x = 1,328.58/31.31
6. Step 6: Final answer
   x = 42.43