Finding the Fourth Proportional to 42.09, 57.98 and 31.15

Step by Step Solution

1. Step 1: Write the proportion equation
   42.09 : 57.98 = 31.15 : x
2. Step 2: Convert to fraction form
   42.09/57.98 = 31.15/x
3. Step 3: Cross multiply
   42.09x = 57.98 × 31.15
4. Step 4: Simplify right side
   42.09x = 1,806.23
5. Step 5: Solve for x
   x = 1,806.23/42.09
6. Step 6: Final answer
   x = 42.92