Home / 420-489

Finding the Third Proportional to 420 and 489

Calculator

Solution

The third proportional to 420 and 489 is: 569.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    420 : 489 = 489 : x
  2. Step 2: Convert to fraction form
    420/489 = 489/x
  3. Step 3: Cross multiply
    420x = 489 × 489
  4. Step 4: Simplify right side
    420x = 239,121
  5. Step 5: Solve for x
    x = 239,121/420
  6. Step 6: Final answer
    x = 569.34

Related Problems

Find third proportional to 210 and 244.50
Half scale
Find third proportional to 840 and 978
Double scale
Find third proportional to 422 and 491
Similar ratio
Find third proportional to 630 and 733.50
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.16) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.