No. of men required is directly proportional to no. of women required and no. of children required in the ratio 1:2:4
men : children = 1 : 4 therefore 4 children can complete 1 man's job in same amt of time
similarly women : children = 1 : 2 so 2 children can complete 1 woman's job in same amt of time
therefore 1 man and 1 woman can be replaced with 6 children
so 1 man, 1 women, 2 children is the same as 8 children
8 children require 10 days to do the work
therefore 1 man, 1 woman, 2 children need 10 days to do the work