RRB NTPC 28 April 2016 Paper

Question : 14 of 100

Marks: +1, -0

Adil and Biren together can complete a task in 20 days. Biren and Chirag together can complete the same task in 50 days. Adil and Chirag together can complete the same task in 40 days. If the same task was to be done by them alone, what would be the ratio of time taken by Adil alone to the time taken by Biren?

11:9
11:3
7:9
9:11

Validate

Solution:

(4) No. of days Adil (A) and Biren (B)together takes = 20 days
No. of days Biren (B) and Chirag (C)takes = 50 days
No. of days Adil (A) and Chirag (C)takes = 40 days
The total work done = LCM of (20,50, 40) = 200
Work Done by A + B in a day
=

200 /20

= 10unit
Work done by B and C in a day
=

200/ 50

= 40 unit
Work done by A and C in a day
=

200 /40

= 5unit
Hence, A + B = 10 ...(i)
B + C = 4 ...(ii)
A + C = 5 ...(iii)
Solving simultaneously equation (i),(ii) & (iii), we get
A = 5.5 units in 1 day
B = 4.5 units in 1 day
Total time taken by A

= { { \text "Complete work" } }/ { { \text "Work done in single day" } } = { 200 }/{ 5.5 }

Total Taken time by

{ B } = { 200 }/ { 4.5 }

Ratio of time taken by A to that taken by B

\⇒ { 200 }/ { 5.5 } : { 200 } /{ 4.5 } = 4.5 : 5.5 = 9 : 11

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