Home / 686.21-1,021.11-640.31

Finding the Fourth Proportional to 686.21, 1,021.11 and 640.31

Calculator

Solution

The fourth proportional to 686.21, 1,021.11 and 640.31 is: 952.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.21 : 1,021.11 = 640.31 : x
  2. Step 2: Convert to fraction form
    686.21/1,021.11 = 640.31/x
  3. Step 3: Cross multiply
    686.21x = 1,021.11 × 640.31
  4. Step 4: Simplify right side
    686.21x = 653,819.44
  5. Step 5: Solve for x
    x = 653,819.44/686.21
  6. Step 6: Final answer
    x = 952.80

Related Problems

Find fourth proportional to 343.10, 510.55 and 320.15
Half scale
Find fourth proportional to 1,372.41, 2,042.21 and 1,280.61
Double scale
Find fourth proportional to 687.21, 1,022.59 and 641.31
Similar ratio
Find fourth proportional to 1,029.31, 1,531.66 and 960.46
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.