Finding the Fourth Proportional to 91.18, 136.78 and 42.40

Step by Step Solution

1. Step 1: Write the proportion equation
   91.18 : 136.78 = 42.40 : x
2. Step 2: Convert to fraction form
   91.18/136.78 = 42.40/x
3. Step 3: Cross multiply
   91.18x = 136.78 × 42.40
4. Step 4: Simplify right side
   91.18x = 5,799.47
5. Step 5: Solve for x
   x = 5,799.47/91.18
6. Step 6: Final answer
   x = 63.60