Finding the Fourth Proportional to 72.88, 100.58 and 72.18

Step by Step Solution

1. Step 1: Write the proportion equation
   72.88 : 100.58 = 72.18 : x
2. Step 2: Convert to fraction form
   72.88/100.58 = 72.18/x
3. Step 3: Cross multiply
   72.88x = 100.58 × 72.18
4. Step 4: Simplify right side
   72.88x = 7,259.50
5. Step 5: Solve for x
   x = 7,259.50/72.88
6. Step 6: Final answer
   x = 99.61