Home / 121.80-168.08-78.16

Finding the Fourth Proportional to 121.80, 168.08 and 78.16

Calculator

Solution

The fourth proportional to 121.80, 168.08 and 78.16 is: 107.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.80 : 168.08 = 78.16 : x
  2. Step 2: Convert to fraction form
    121.80/168.08 = 78.16/x
  3. Step 3: Cross multiply
    121.80x = 168.08 × 78.16
  4. Step 4: Simplify right side
    121.80x = 13,137.13
  5. Step 5: Solve for x
    x = 13,137.13/121.80
  6. Step 6: Final answer
    x = 107.86

Related Problems

Find fourth proportional to 60.90, 84.04 and 39.08
Half scale
Find fourth proportional to 243.60, 336.16 and 156.32
Double scale
Find fourth proportional to 122.80, 169.46 and 79.16
Similar ratio
Find fourth proportional to 182.70, 252.12 and 117.24
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.