Finding the Third Proportional to 990 and 1,678.50

Step by Step Solution

1. Step 1: Write the proportion equation
   990 : 1,678.50 = 1,678.50 : x
2. Step 2: Convert to fraction form
   990/1,678.50 = 1,678.50/x
3. Step 3: Cross multiply
   990x = 1,678.50 × 1,678.50
4. Step 4: Simplify right side
   990x = 2,817,362.25
5. Step 5: Solve for x
   x = 2,817,362.25/990
6. Step 6: Final answer
   x = 2,845.82