Finding the Fourth Proportional to 105.42, 145.47 and 72.70

Step by Step Solution

1. Step 1: Write the proportion equation
   105.42 : 145.47 = 72.70 : x
2. Step 2: Convert to fraction form
   105.42/145.47 = 72.70/x
3. Step 3: Cross multiply
   105.42x = 145.47 × 72.70
4. Step 4: Simplify right side
   105.42x = 10,575.67
5. Step 5: Solve for x
   x = 10,575.67/105.42
6. Step 6: Final answer
   x = 100.32