Finding the Fourth Proportional to 99.72, 137.54 and 72.12

Step by Step Solution

1. Step 1: Write the proportion equation
   99.72 : 137.54 = 72.12 : x
2. Step 2: Convert to fraction form
   99.72/137.54 = 72.12/x
3. Step 3: Cross multiply
   99.72x = 137.54 × 72.12
4. Step 4: Simplify right side
   99.72x = 9,919.02
5. Step 5: Solve for x
   x = 9,919.02/99.72
6. Step 6: Final answer
   x = 99.47