Latest Elitmus Aptitude Question SOLUTION: obama can build a wall in 21 months and osama can destroy in 28 months,they worked alternately .in how many days they will complete the work? a)161b)168c)167d)163

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(#M40040364) ELITMUS Numerical Ability question time and work Keep an EYE

obama can build a wall in 21 months and osama can destroy in 28 months,they worked alternately .in how many days they will complete the work?
a)161b)168c)167d)163

Asked In Elitmus amit (9 years ago)

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kumar  (9 years ago)

obama build in 21 months
osama sala terorist and destructor 28 months

take lcm of 21 and 28 =7*3*4 unit=total work
so obama efficency =7*3*4 /21=+4 (+ for construction)
osama(terorist) destructor =-7*3*4/28 =-3(constructor)

now in two day they will work 4-3=1 unit and total work=84 unit
now part of concentration
if they will work for 80 day each then work completed =80 unit
and now obama wark for a day then total work will be =80+4 =84 ,mean building complete
so total time =80+80+1=161 months
thanks this logic is taken from NCERT book of class 8 or 9

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amit  (9 years ago)

i think 161 is the answer...

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aditya saraswat  (9 years ago)

A=100/21=4.761,B=100/28=3.5718(-ve work)
total=4.761-3.5718=1.19047
time to complete 96% of work=96/1.19047=80month due to altenate work total month=2*80=160
now for next one month the work get completed
so total month of work=160+1=161

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Neema Pal  (9 years ago)

Take lcm 0f 21 and 28=84 units
obama can do 84 units of work in 21 months
in 1 month,he will complete 4 units of total work i.e 84/21=4
similarly osama can destory 84 units of work in28 months
in 1 month, he will destory 3 units of work i.e 84/28=3
working alternately , obama built the 4 units of wall in first month
osama destroy the 3 units of wall in the second month
total work done in 2 months is 1 unit i.e 4-3=1
therefore, 84 pairs of month is needed for work to be done
hence in 168 months they will complete the work

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rajeev chaubey  (9 years ago)

ans-161 month explained already

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aditya saraswat  (9 years ago)

A=100/21=4.761 and B=100/28=3.5718(-ve)
there net work=1.19047
total days=2*100/1.19047=168days

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