Question

54. A and B together can do a piece of work in 12 days, while B
alone can finish it in 30 days. A alone can finish the work in
(a) 15 days
(b) 18 days
(c) 20 days
(d) 25 days​

Answer 1

Answer:

30 days

Step-by-step explanation:

Given ,

the number of days taken by A and B together complete the work = 12 days

and B can finish the work = 30 days

now let the number of days taken by A to complete the work alone be x

the work done by B in one day =1/30

the work done by A in one day =1/x

the total number of days = 1/30+1/x

= x+30

_______

24x

in one day = 30x

_____

x+30

according to question

=> 30x

-------- =12

x+30

=> 12x+12×30 = 24x ( cross multiplication)

=> 12×24= 30x -12x

=>12×30= 12x

=>360=12x

=>360/12=x

=> x = 30