Finding the Fourth Proportional to 124.35, 171.50 and 99.78

Step by Step Solution

1. Step 1: Write the proportion equation
   124.35 : 171.50 = 99.78 : x
2. Step 2: Convert to fraction form
   124.35/171.50 = 99.78/x
3. Step 3: Cross multiply
   124.35x = 171.50 × 99.78
4. Step 4: Simplify right side
   124.35x = 17,111.77
5. Step 5: Solve for x
   x = 17,111.77/124.35
6. Step 6: Final answer
   x = 137.61