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The lengths, in cm, of pencil used by pupils in standard one class on a certain day were recorded as follows. 3 7 9 9 20 14 10 6 8 13 14 3 17 13 8 12 5 15 14 15 7 12 11 6 10 19 9 14 6 9
10 16 13 9 12 11 10 7 10 11
a) Using a class width of 3, and starting with the shortest length of pencil, make a frequency distribution table for the data.
b) Calculate:
(i) the mean length of pencils;
(ii) the percentage of pencil that were longer than 8 cm but shorter than 15 cm.