Home / 72-81

Finding the Third Proportional to 72 and 81

Calculator

Solution

The third proportional to 72 and 81 is: 91.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    72 : 81 = 81 : x
  2. Step 2: Convert to fraction form
    72/81 = 81/x
  3. Step 3: Cross multiply
    72x = 81 × 81
  4. Step 4: Simplify right side
    72x = 6,561
  5. Step 5: Solve for x
    x = 6,561/72
  6. Step 6: Final answer
    x = 91.13

Related Problems

Find third proportional to 36 and 40.50
Half scale
Find third proportional to 144 and 162
Double scale
Find third proportional to 74 and 83
Similar ratio
Find third proportional to 108 and 121.50
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.13) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.