Latest Elitmus Aptitude Question SOLUTION: A basket ball is dropped from a height of 20 feet .It bounces back each time to a height which is one half of the height of the last bounce. How far approximately ball have travell

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(#M40158255) ELITMUS Numerical Ability question Series Keep an EYE

A basket ball is dropped from a height of 20 feet .It bounces back each time to a height which is one half of the height of the last bounce. How far approximately ball have travelled before it comes to rest?

a.30 feet
b.40 feet
c.60 feet
d. can't be determined

Asked In Elitmus Shashank Saha (7 years ago)

Unsolved Read Solution (4)

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shehzad  (7 years ago)

first the ball will travel 20 feet before reaching the ground then it will bounce back to 10 ft nd return to ground covrng 10 ft nd then bounce to 5 ft which will make it an infinite GP with r=1/2
so total distance would be
20 + 20/(1-1/2) =60 ft

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Pradosh Kumar Mohapatra  (7 years ago)

here the basket ball dropped from a height of 20 ft and it bounces back to a height which is half of the height last bounce so it is in G.P
Sn = 20 + 10 + 5 + 2.5 +.......
here a=20
r=1/2
n=∞
in case of r < 1 and n=∞ for such condition
Sn = a/(1-r)
i.e
Sn = 20/(1-1/2)
i.e Sn = 40
so the answer is 40 feet

Is this solution Helpfull? Yes (2) | No (1)  

Lokesh  (7 years ago)

20+10+10+5+5+2,5+2.5+1.25+1.25+0.75+0.75=60

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Manisha Choudhary  (7 years ago)

sum of infinite GP
where a = 20 and r = 1/2
ANS 60

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