X | 18 | 20 | 25 | 30 | 34 | 38 | 40 |
F | 6 | 7 | 3 | 7 | 7 | 5 | 5 |
Draw the table as below,
(x) | (f) | Cumulative frequency | Fx |
18 | 6 | 6 | 108 |
20 | 7 | 13 | 140 |
25 | 3 | 16 | 75 |
30 | 7 | 23 | 210 |
34 | 7 | 30 | 238 |
38 | 5 | 35 | 190 |
40 | 5 | 40 | 200 |
N = 40 | ∑fx = 1161 |
We have;
N = 40 (even number)
Median = 
Now,
∑fx = 1161 and ∑f = N = 40
Mean = 
Hence,
Mode = 3(median) – 2 (mean)
= 3×30 - 2×29
= 90 - 68
= 32
8