Home / 85-109

Finding the Third Proportional to 85 and 109

Calculator

Solution

The third proportional to 85 and 109 is: 139.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    85 : 109 = 109 : x
  2. Step 2: Convert to fraction form
    85/109 = 109/x
  3. Step 3: Cross multiply
    85x = 109 × 109
  4. Step 4: Simplify right side
    85x = 11,881
  5. Step 5: Solve for x
    x = 11,881/85
  6. Step 6: Final answer
    x = 139.78

Related Problems

Find third proportional to 42.50 and 54.50
Half scale
Find third proportional to 170 and 218
Double scale
Find third proportional to 87 and 112
Similar ratio
Find third proportional to 127.50 and 163.50
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.28) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.