Home / 689-1,290

Finding the Third Proportional to 689 and 1,290

Calculator

Solution

The third proportional to 689 and 1,290 is: 2,415.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    689 : 1,290 = 1,290 : x
  2. Step 2: Convert to fraction form
    689/1,290 = 1,290/x
  3. Step 3: Cross multiply
    689x = 1,290 × 1,290
  4. Step 4: Simplify right side
    689x = 1,664,100
  5. Step 5: Solve for x
    x = 1,664,100/689
  6. Step 6: Final answer
    x = 2,415.24

Related Problems

Find third proportional to 344.50 and 645
Half scale
Find third proportional to 1,378 and 2,580
Double scale
Find third proportional to 691 and 1,294
Similar ratio
Find third proportional to 1,033.50 and 1,935
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.87) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.