100m Race A stopwatch was used to find the time that it took a group of students to run 100m

i) Estimate the mean time taken by a student to finish the race
54
63
43
50
(ii) The construction of commulative frequency table is useful in determining the
Mean
Median
Mode
All of the above
(iii) What will be the upper limit of the modal class ?
20
40
60
80
(iv) How many students finished the race within 1 minute?
18
77
60
45
Answers
Answer:
the correct answer is option number first one second 6460
Given : A stopwatch was used to find the time that it took a group of students to run 100 m.
Time (in sec) 0-20 20-40 40-60 60-80 80-100
No. of students 17 28 32 24 19
To Find : Estimate the mean time taken by a student to finish the race
Solution:
The construction of cumulative frequency table is useful in determining the Median
Time (in sec) f cf
0-20 17 17
20-40 28 45
40-60 32 77
60-80 24 101
80-100 19 120
1 minute = 60 sec
Time less than 60 sec = 77 Students
77 students finished the race within 1 minute
mean time taken by a student to finish the race = (10*17 + 30*28+50*32+70*24+90*19)/120
= (170 + 840 + 1600 + 1680 + 1710)/120
= (17 + 84 + 160 + 168 + 171 )/12
= 590/12
= 49.2
= 50 secs
40-60 is modal class hence upper limit of modal class = 60
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