How many students finished the race within 1 minute?
(i)18
(ii)37
(iii)31
(iv)8
Part –B
All questions are compulsory. In case of internal choices, attempt any
one.
21.
3 bells ring at an interval of 4,7 and 14 minutes. All three bell rang at 6 am,
when the three balls will the ring together next?
2
22.
Find the point on x-axis which is equidistant from the points (2,-2) and (-4,2)
Answers
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 8 10 13 6 3
To Find : How many students finished the race within 1 minute?
(i)18
(ii)37
(iii)31
(iv)8
Solution:
Time (in sec) f cf
0-20 8 8
20-40 10 18
40-60 13 31
60-80 6 37
80-100 3 40
1 minute = 60 sec
Time less than 60 sec = 31 Students
31 students finished the race within 1 minute
option iii) is correct
3 bells ring at an interval of 4,7 and 14 minutes. All three bell rang at 6 am,
LCM of 4 , 7 & 14 = 28
three balls will the ring together next at 6:28 AM
point on x-axis which is equidistant from the points (2,-2) and (-4,2)
√(x - 2)² + (0 -(-2))² =√ (x -(-4))² + (0 - 2)²
=> (x - 2)² + 4 = (x +4)² + 4
=> x² - 4x + 4 = x² + 16 + 8x
=> 12x = - 12
=> x = - 1
Point is (-1 , 0) is equidistant from the points (2,-2) and (-4,2)
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