Finding the Fourth Proportional to 99.99, 137.96 and 56.31

Step by Step Solution

1. Step 1: Write the proportion equation
   99.99 : 137.96 = 56.31 : x
2. Step 2: Convert to fraction form
   99.99/137.96 = 56.31/x
3. Step 3: Cross multiply
   99.99x = 137.96 × 56.31
4. Step 4: Simplify right side
   99.99x = 7,768.25
5. Step 5: Solve for x
   x = 7,768.25/99.99
6. Step 6: Final answer
   x = 77.69