Finding the Fourth Proportional to 972.10, 1,339.89 and 688.15

Step by Step Solution

1. Step 1: Write the proportion equation
   972.10 : 1,339.89 = 688.15 : x
2. Step 2: Convert to fraction form
   972.10/1,339.89 = 688.15/x
3. Step 3: Cross multiply
   972.10x = 1,339.89 × 688.15
4. Step 4: Simplify right side
   972.10x = 922,045.30
5. Step 5: Solve for x
   x = 922,045.30/972.10
6. Step 6: Final answer
   x = 948.51