Latest zs Aptitude Question SOLUTION: Amith starts to work on the first day. On the second day two more friends join him. On the third day 3 more friends join him and so on they complete work in 30 days. The find the n

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(#M40164987) ZS Numerical Ability question Keep an EYE

Amith starts to work on the first day. On the second day two more friends join him. On the third day 3 more friends join him and so on they complete work in 30 days. The find the number of days 16 girls can finish the work completely given that a girl can work twice as fast as Amith and his friends

Asked In zs gunjan (6 years ago)

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  (6 years ago)

155 days.

Let Amith or his friend alone can complete the work in 'x' days, then
1 day work of Amith=1 day work of his friend=1/x
Their 30 day's work=1/x + 3/x + 6/x + 10/x .... =1
=> 1/x (1 + 3 + 6 + 10 +....upto 30 terms)=1
Sequence 1,3,6,10,15,... is called triangle number series with sum=n(n+1)(n+2)/6
=> (1/x) (30*31*32/2) =1
=> 1/x=1/4960
As girl is of twice capacity of a boy, so 1 girl's 1 day work = 2*(1/x)=2*1/4960=1/2480
So 16 girl's 1 day work=16*(1/2480)=1/155
Hence required days=155

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