a can do a piece of work in 100 days, b and c together can do the same work in 20 days. if b can do the work in same time as that of c and a  together then how long c alone can do the same work?

 

a) 100 days     
b) 50days     
c) 25days     
d) 20 days

 

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50 days is correct

Step-by-step explanation:

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700

A can do a piece of work in 100 days

⇒ 1 day = 1/100

⇒ 1/a = 1/100

B and C can do the work in 20 days

⇒ 1 day = 1/20

⇒ 1/b + 1/c = 1/20

B can do the work in the same time as C and A

⇒ 1/b = 1/c + 1/100

⇒ 1/b - 1/c = 1/100

1/b + 1/c = 1/20 [ 1 ]

1/b - 1/c = 1/100 [ 2 ]

[ 1 ] + [ 2 ]:

2/b = 3/50

3b = 100

b = 100/3

FInd c:

1/b + 1/c = 1/20 [ From [1] ]

3/100 + 1/c = 1/20

1/c = 1/20 - 3/100

1/c = 1/50

Number of days c need:

1/c = 1/50

c = 50 days

C needs 50 days

C alone can do the same work in 50 days.

Step-by-step explanation:

It is given that A can do a piece of work in 100 days. The part of work done by  A in 1 day is .

The part of work done by B and C in one day is and respectively.

It is given that B and C together can do the same work in 20 days.

         ..... (1)

B can do the work in same time as that of C and A together.

        ..... (2)

Subtract equation (2) from (1).

Since c=50, therefore c alone can do the same work in 50 days.

it is given can a is do the work in hundred days is it is 1 given thatc, she was alone is x and BC is complete the work in 20 days show the C works is equals to1/b+1/c =1/20

Step-by-step explanation:

1/b=1/a+1/c1/b1/c=1/100 now,subtract the equation 1from 2 1/b+1/c-(1/b_1/c)=1/20-1/100 then,take common 1/c that is ,2(1/c)=4/100 hence, 2(1/c)=1/25 ,then1/c=1/50 c=50 so,that C done works alone in 50 days

Step-by-step explanation:

answer

C can do the work in 15days alone which A can do in 100 days