Home / 643.78-821.39

Finding the Third Proportional to 643.78 and 821.39

Calculator

Solution

The third proportional to 643.78 and 821.39 is: 1,048.00

Step by Step Solution

  1. Step 1: Write the proportion equation
    643.78 : 821.39 = 821.39 : x
  2. Step 2: Convert to fraction form
    643.78/821.39 = 821.39/x
  3. Step 3: Cross multiply
    643.78x = 821.39 × 821.39
  4. Step 4: Simplify right side
    643.78x = 674,682.56
  5. Step 5: Solve for x
    x = 674,682.56/643.78
  6. Step 6: Final answer
    x = 1,048.00

Related Problems

Find third proportional to 321.89 and 410.70
Half scale
Find third proportional to 1,287.56 and 1,642.78
Double scale
Find third proportional to 646 and 824
Similar ratio
Find third proportional to 965.67 and 1,232.09
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.