Home / 10.80-16.20-7.80

Finding the Fourth Proportional to 10.80, 16.20 and 7.80

Calculator

Solution

The fourth proportional to 10.80, 16.20 and 7.80 is: 11.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    10.80 : 16.20 = 7.80 : x
  2. Step 2: Convert to fraction form
    10.80/16.20 = 7.80/x
  3. Step 3: Cross multiply
    10.80x = 16.20 × 7.80
  4. Step 4: Simplify right side
    10.80x = 126.36
  5. Step 5: Solve for x
    x = 126.36/10.80
  6. Step 6: Final answer
    x = 11.70

Related Problems

Find fourth proportional to 5.40, 8.10 and 3.90
Half scale
Find fourth proportional to 21.60, 32.40 and 15.60
Double scale
Find fourth proportional to 11.80, 17.70 and 8.80
Similar ratio
Find fourth proportional to 16.20, 24.30 and 11.70
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.