Question

A and B can do a piece of work in 12 days, B and C can do it in 15 days while C and A can finish it in 20days. In how many days can A finish the job

Answer 1

a+b= 12days

b+c=15days

c+a=20days

total work = L.C.M of 12,15,20 = 60

a+b's 1 day work= 60/12=5 unit

b+c's .....................= 4 unit

c+a's .......... = 3 unit

adding all 2(a+b+c)=5+4+3

a+b+c=12/2

a+b+c=6 unit ..................... equation (1)

put b+c =4 in equation (1)

a= 2 unit/day

to complete 60 unit work , time taken by a = 60/2=30day

Answer 2

Step-by-step explanation:

ANSWER

Let the tens digit of the required number be x and the units digit be y. Then,

x+y=12 .........(1)

Required Number = (10x+y).

Number obtained on reversing the digits = (10y+x).

Therefore,

(10y+x)−(10x+y)=18

9y−9x=18

y−x=2 ..........(2)

On adding (1) and (2), we get,

2y=14⟹y=7

Therefore,

x=5

Hence, the required number is 57.