Question

A is 60% more efficient than B. How much time will they, working together, take to complete a job which A alone could have done in 28 days?
A) 20 days
B) 23 days
C) 17313 days
D) 26 days
E) None of these

Answer 1

efficiency and time are inverse

A is 60% faster than B

160:100 is x X 28

B work efficiency is 224/5

A 1 day work =1/28

B. 1 day work is 5/224

add both to get A+B as 17 3/13. which is C

Answer 2

Answer:

$17\frac{3}{13} \:days$

option C

Step-by-step explanation:

A is 60% more efficient than B. How much time will they, working together, take to complete a job which A alone could have done in 28 days?

A) 20 days

B) 23 days

C) 17313 days

D) 26 days

E) None of these

A alone could do in 28 days

A's 1 day work = 1/28

Let say B's 1 day work = B

A is 60% more efficient than B

so A's 1 day Work = B's 1 day work + 60% of B's 1 day work

1/28 = B + (60/100)B

=> 1/28 = 8/5B

=> B = 5/(28 * 8)

=> B = 5/224

A + B together 1 day work =  1/28 + 5/224

= (8 + 5)/224

= 13/224

Time taken to complete job = 1/(13/224)  = 224/13

=$17\frac{3}{13}$

option C