Home / 15.79-21.81-15.55

Finding the Fourth Proportional to 15.79, 21.81 and 15.55

Calculator

Solution

The fourth proportional to 15.79, 21.81 and 15.55 is: 21.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.79 : 21.81 = 15.55 : x
  2. Step 2: Convert to fraction form
    15.79/21.81 = 15.55/x
  3. Step 3: Cross multiply
    15.79x = 21.81 × 15.55
  4. Step 4: Simplify right side
    15.79x = 339.15
  5. Step 5: Solve for x
    x = 339.15/15.79
  6. Step 6: Final answer
    x = 21.48

Related Problems

Find fourth proportional to 7.90, 10.91 and 7.78
Half scale
Find fourth proportional to 31.58, 43.62 and 31.10
Double scale
Find fourth proportional to 16.79, 23.19 and 16.55
Similar ratio
Find fourth proportional to 23.69, 32.72 and 23.33
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.