one man started a work on first day, the second day one more joined with him the next day one more joined everyday one new person joined until work get completed. if the work is completed in 15 days how many days it takes for 10 men to complete the same work if they joined regularly?
Answers
Answer:
7 and 1/2 day
Step-by-step explanation:
1+2+3+....+N = 15
formula :
Sn= n/2 { 2a + (n-1)d }
15 = N/2 {2+N-1}
15 = N/2 {N+1}
30 = N ( N+1 )
30 = 5 ( 5+1 )
30 = 30
Here by N = 5
5 persons can do the work in 15 days,
10 persons can do the work in 15/2 = 7 1/2 days.
Step-by-step explanation:
on first day number of men = 1
work completed = 1
on second day number of men = 2
work completed = 2
on third day number of men = 3
work completed = 3
total work in 15 days = Sn = n/2 {2a+(n-1)d}
a = 1 = work on first day
Sn = 15 = total days
d = 1 = difference in every succeeding day's work
15= n/2 {2(1) +(n-1)1}
30 = n {2+n-1}
30 = n ( 1+n )
let the value of n be 5 so that his equation satisfied on both sides
30 = 5 (1 + 5)
30 = 5× 6
30 = 30
n= 5 work completed in 15 days
if n = 10 then work completed will be 15/2 = 7.5 days