One man started a work on first day, the second day one more joined him. The next day one more joined. Everyday one new person joined until the work got completed. If the work is completed in 15 days, how many days do 10 men take to complete the same work, if they work regularly?

Question

anonymous · Answer

i think it is in 10 days ah

loser66 · Answer

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got me so far?

loser66 · Answer

the total work is 120 parts
$$\sum_1^{15}i$$

loser66 · Answer

1 man works 1part/day
10 men work 10parts/day
10 men work 120 parts in how many days????

loser66 · Answer

let me count my fingers to you ( the simplest way to understand)
10 men work 10parts/day
on 10 days, they work 100 parts
still have 20 parts, right? they need 2more days. 
10days +2 days =12 days
that's what I think. hehehe

loser66 · Answer

hey!! message me to get help and say nothing ??? how can I know you get it or not?

loser66 · Answer

I don't know what you are talking about and how you get the expression,