Home / 427.20-640.80-409.20

Finding the Fourth Proportional to 427.20, 640.80 and 409.20

Calculator

Solution

The fourth proportional to 427.20, 640.80 and 409.20 is: 613.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    427.20 : 640.80 = 409.20 : x
  2. Step 2: Convert to fraction form
    427.20/640.80 = 409.20/x
  3. Step 3: Cross multiply
    427.20x = 640.80 × 409.20
  4. Step 4: Simplify right side
    427.20x = 262,215.36
  5. Step 5: Solve for x
    x = 262,215.36/427.20
  6. Step 6: Final answer
    x = 613.80

Related Problems

Find fourth proportional to 213.60, 320.40 and 204.60
Half scale
Find fourth proportional to 854.40, 1,281.60 and 818.40
Double scale
Find fourth proportional to 428.20, 642.30 and 410.20
Similar ratio
Find fourth proportional to 640.80, 961.20 and 613.80
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.