After completion 50% of work a alone,b joins him and the work was completed 4 days earlier.If b alone can do50% in 15 days,find (a+b) together time
Answers
Answer:
12 Days
Step-by-step explanation:
After completion 50% of work a alone,b joins him and the work was completed 4 days earlier.If b alone can do 50% in 15 days,find (a+b) together time
B can do 50% work in 15 days
=> B can completed work in 30 days
=> B's 1 day work = 1/30
Let Say A complete work in A days
A's 1 day work = 1/A
50% work will be done in A/2 Days
Remaining work for A/2 days and finished 4 days earlier
=> a + b Did work for A/2 - 4 Days
a + b's 1 (A/2 - 4) days work
= (A/2 -4)/A + (A/2 -4 )/30
= (A - 8)(1/A + 1/30)/2
Remaining work was to be done = 1/2
=> (A - 8)(1/A + 1/30)/2 = 1/2
=> ( A - 8) (30 + A)/30A = 1
=> A² + 22A - 240 = 30A
=>A² - 8A - 240 = 0
=> A² - 20A + 12A - 240 = 0
=> A(A -20) + 12(A - 20) = 0
=> A = 20 ( -ve value discarded)
A's 1 day work = 1/20
B's 1 day work = 1/30
A + B's 1 day work = 1/20 + 1/30 = 5/60 = 1/12
A + B together can complete work in 12 Days
Answer:
20
Step-by-step explanation:
let the half of the work done by A = x days
(x-4)/15=4/x
-4x-60=0
(x-10)(x+6)=0
so x=10 and whole work = 2x=20