Finding the Fourth Proportional to 91.72, 137.55 and 78.97

Step by Step Solution

1. Step 1: Write the proportion equation
   91.72 : 137.55 = 78.97 : x
2. Step 2: Convert to fraction form
   91.72/137.55 = 78.97/x
3. Step 3: Cross multiply
   91.72x = 137.55 × 78.97
4. Step 4: Simplify right side
   91.72x = 10,862.32
5. Step 5: Solve for x
   x = 10,862.32/91.72
6. Step 6: Final answer
   x = 118.43