Home / 258.70-388.18-128.70

Finding the Fourth Proportional to 258.70, 388.18 and 128.70

Calculator

Solution

The fourth proportional to 258.70, 388.18 and 128.70 is: 193.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.70 : 388.18 = 128.70 : x
  2. Step 2: Convert to fraction form
    258.70/388.18 = 128.70/x
  3. Step 3: Cross multiply
    258.70x = 388.18 × 128.70
  4. Step 4: Simplify right side
    258.70x = 49,958.77
  5. Step 5: Solve for x
    x = 49,958.77/258.70
  6. Step 6: Final answer
    x = 193.11

Related Problems

Find fourth proportional to 129.35, 194.09 and 64.35
Half scale
Find fourth proportional to 517.40, 776.36 and 257.40
Double scale
Find fourth proportional to 259.70, 389.68 and 129.70
Similar ratio
Find fourth proportional to 388.05, 582.27 and 193.05
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.