Finding the Fourth Proportional to 72.42, 99.99 and 57.90

Step by Step Solution

1. Step 1: Write the proportion equation
   72.42 : 99.99 = 57.90 : x
2. Step 2: Convert to fraction form
   72.42/99.99 = 57.90/x
3. Step 3: Cross multiply
   72.42x = 99.99 × 57.90
4. Step 4: Simplify right side
   72.42x = 5,789.42
5. Step 5: Solve for x
   x = 5,789.42/72.42
6. Step 6: Final answer
   x = 79.94