Missing Frequency 3D4D21
1. **State the problem:** We are given a frequency distribution with a missing frequency and the mean of the data is 22. We need to find the missing frequency.
2. **Given data:**
Central values (x): 10, 15, 20, 25, 30
Frequencies (f): 5, 10, 15, ?, 5
Mean (\(\bar{x}\)) = 22
3. **Formula for mean:**
$$\bar{x} = \frac{\sum f_i x_i}{\sum f_i}$$
4. **Let the missing frequency be** $f$.
5. **Calculate the sum of frequencies:**
$$\sum f_i = 5 + 10 + 15 + f + 5 = 35 + f$$
6. **Calculate the sum of products of frequencies and values:**
$$\sum f_i x_i = 5 \times 10 + 10 \times 15 + 15 \times 20 + f \times 25 + 5 \times 30$$
$$= 50 + 150 + 300 + 25f + 150 = 650 + 25f$$
7. **Use the mean formula:**
$$22 = \frac{650 + 25f}{35 + f}$$
8. **Multiply both sides by** $35 + f$:
$$22(35 + f) = 650 + 25f$$
$$770 + 22f = 650 + 25f$$
9. **Rearrange to solve for** $f$:
$$770 - 650 = 25f - 22f$$
$$120 = 3f$$
$$f = \frac{120}{3} = 40$$
**Final answer:** The missing frequency is **40**.