1. **State the problem:** We are given a frequency distribution of masses of maize flour used by 30 traders and asked to find the median mass. 2. **Recall the formula for median in grouped data:** $$\text{Median} = L + \left(\frac{\frac{n}{2} - F}{f}\right) \times c$$ where: - $L$ = lower boundary of the median class - $n$ = total number of observations - $F$ = cumulative frequency before the median class - $f$ = frequency of the median class - $c$ = class width 3. **Calculate cumulative frequencies:** - Class 10-19: frequency = 3, cumulative frequency = 3 - Class 20-29: frequency = 8, cumulative frequency = 3 + 8 = 11 - Class 30-39: frequency = 10, cumulative frequency = 11 + 10 = 21 - Class 40-49: frequency = 7, cumulative frequency = 21 + 7 = 28 - Class 50-59: frequency = 2, cumulative frequency = 28 + 2 = 30 4. **Find the median class:** - Total $n = 30$ - $\frac{n}{2} = 15$ - The cumulative frequency just greater than or equal to 15 is 21 (class 30-39) - So, median class is 30-39 5. **Identify values for the formula:** - $L = 30$ (lower boundary of median class) - $F = 11$ (cumulative frequency before median class) - $f = 10$ (frequency of median class) - $c = 10$ (class width, 39 - 30 + 1 = 10 assuming continuous classes) 6. **Calculate the median:** $$\text{Median} = 30 + \left(\frac{15 - 11}{10}\right) \times 10 = 30 + \left(\frac{4}{10}\right) \times 10 = 30 + 4 = 34$$ **Final answer:** The median mass of maize flour sold is **34 kg**.