Home / 138-209

Finding the Third Proportional to 138 and 209

Calculator

Solution

The third proportional to 138 and 209 is: 316.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    138 : 209 = 209 : x
  2. Step 2: Convert to fraction form
    138/209 = 209/x
  3. Step 3: Cross multiply
    138x = 209 × 209
  4. Step 4: Simplify right side
    138x = 43,681
  5. Step 5: Solve for x
    x = 43,681/138
  6. Step 6: Final answer
    x = 316.53

Related Problems

Find third proportional to 69 and 104.50
Half scale
Find third proportional to 276 and 418
Double scale
Find third proportional to 140 and 212
Similar ratio
Find third proportional to 207 and 313.50
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.