Question

Pranalee was practising for a 100 m running race. She ran 100 m distance 20 times. The time required, in seconds, for each attempt was as follows:
18, 17, 17, 16, 15, 16, 15, 14, 16, 15, 15, 17, 15, 16, 15, 17, 16, 15, 14, 15 Find the mean of the times taken for running.

Answer 1

Time in seconds (xi)	Tally marks	No. of attempts (fi)	fi × xi
14	||	2	28
15	`cancel(bb|bb|bb|bb|)` |||	8	120
16	`cancel(bb|bb|bb|bb|)`	5	80
17	||||	4	68
18	|	1	18
		N = 20	`bb(sumf_ix_i = 314)`

Mean `(barx) = (sumf_ix_i)/"N"`

= `314/20`

= 15.7 seconds

∴ The mean of the time taken for running a 100 m race is 15.7 seconds.