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prajakta

· started a discussion

· 1 Months ago

answer option should be E not D (question 88676.0) (Question: 88676.0 )

A+B=20
B+C=30
A+C=40
2(A+B+C)=90
A+B+C=90/2=45
A=15 B=5 C=25
A:B=3:5

Question:

A and B together can complete a task in 20 days. B and C together can complete the same task in 30 days. A and C together can complete the same task in 40 days. What is the ratio of the number of days taken by A when completing the same task alone to the number of days taken by C when completing the same task alone?       

Options:
A) 2 : 5   
B) 2 : 7 
C) 3 : 7
D) 1 : 5 
E) 3 : 5
Solution:
Ans(d)


Snehlata

· commented

· 1 Months ago

@Prajakta
You are applying short trick but in a wrong way
It works like this:

Take the LCM of 20,30,40 i.e 120 ,then

A+B= 6 (bcz 20*6=120)--eq1
B+C= 4 (bcz 30*4=120)--eq2
A+C= 3 (bcz 40*3=120)--eq3

Adding equation 1,2 and 3
2(A+B+C)=13

A+B+C=13/2 so we get A=5/2 and C=1/2 so A:C=5:1

kanhaiya jha

· commented

· 1 Months ago

Exactly @Sonam...1:5 is the correct answer....:)

Sonam Rastogi

· commented

· 1 Months ago

YOU ARE WRONG
...............................................
A+B=20
B+C=30
C+A=40
We have to take the LCM of these no.s(20,30,40)
LCM = 120
A+B =6, A+B can do 6 work in 1 day
B+C =4, B+C can do 4 work in 1 day
C+A =3, C+A can do 3 work in 1 day
2(A+B+C)=13
A+B+C=13/2 = 6.5
SO, A=2.5, and C=0.5
A:B=2.5:0.5
=25 : 5
=5:1
Efficiency = 5:1
so Time = 1:5

mounika

· commented

· 1 Months ago

better solution

vinod

· commented

· 1 Months ago

If A & B finish the work in 20 days. How can A,B &C all together finish the same job in 45 days?, the job must be finished by them in less than 20 days

kanhaiya jha

· commented

· 1 Months ago

1:5 is correct answer....please click on report and view solution...
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