Question

(29) 20 men can do a job in 20 days. After each day, a man is replaced by a woman and a woman is twice efficient as
a man. On which day does the job get completed?
a) 14th day
b) 15th day
c) 20th day
d) 24th day
e) Can't say​

Answer 1

my answer is e ) can't say

sorry

Answer 2

Answer:

15

Step-by-step explanation:

let's assume total work is = 400 units

20 men takes 20 days to complete the work .

so everyday work done = 20 units .

1unit / per man

every man = 1 unit work .

a woman is twice efficient.

so she will do = 2 units of work/day.

day 1 = 20 unit.

day 2= 19 men + 1 woman = 19 unit work + 2units = 21

day 3= 18 men + 2 women = 18 unit work + 4units= 22

...

..

..

so on until 400 unit of assumed work is over .

so ans is 15 days .

how to find 15 ?

1. by adding of course..

or

2. first 14 digit sum = n(n+1)/2 = 14*15/2= 105

and 20*15= 300 ( cuz we need 300 more for 400 units of work common sense ) and

on last day they will do 29 unit of remaining work although they have capacity of 34 unit work that day .)

20+21+22+23...+34 = here we are adding 20's 15 times = 300 along with 1+2+3+4...+14=105

I think it's a detailed explanation . I hope it will be helpful.