Finding the Fourth Proportional to 91.89, 137.52 and 78.30

Step by Step Solution

1. Step 1: Write the proportion equation
   91.89 : 137.52 = 78.30 : x
2. Step 2: Convert to fraction form
   91.89/137.52 = 78.30/x
3. Step 3: Cross multiply
   91.89x = 137.52 × 78.30
4. Step 4: Simplify right side
   91.89x = 10,767.82
5. Step 5: Solve for x
   x = 10,767.82/91.89
6. Step 6: Final answer
   x = 117.18