Finding the Fourth Proportional to 100.78, 151.18 and 91.80

Step by Step Solution

1. Step 1: Write the proportion equation
   100.78 : 151.18 = 91.80 : x
2. Step 2: Convert to fraction form
   100.78/151.18 = 91.80/x
3. Step 3: Cross multiply
   100.78x = 151.18 × 91.80
4. Step 4: Simplify right side
   100.78x = 13,878.32
5. Step 5: Solve for x
   x = 13,878.32/100.78
6. Step 6: Final answer
   x = 137.71