**Sol : **In this kind of questions we find the work force required to complete the work in 1 day (or given unit of time) then we equate the work force to find the relationship between the efficiencies (or work rate) between the different workers.

Therefore, 6B+8G = 6 days

=> 6(6B+8G)= 1 day (inversely proportional)

=> 36B+48G =1 ( by unitary method)

Again 14B+10G = 4days

=> 56B+40G =1

so, here it is clear that either we employ 36B and 48G to finish the work in 1 day or 56B and 40G to finish the same job in 1 day. thus , we can say

=> 36B+48G = 56B+40G

=> G= 2.5B

Thus a Girl is 2.5 times as efficient as a boy.

Now, since 36B+48G = 1

=> 36B+48(2.5 B)=1

=>156B=1

i.e., to finish the job in 1 day 156 boys are required or the amount of work is 156 boys-days

Again 1G+1B=2.5B+1B=3.5B

Now, since 156 boys can finish the job in 1 day

so 1 boy can finish the job in 156 days

Therefore, 3.5 boys can finish the job in $\frac{1\times 156}{3.5}=\frac{4}{7}$ days.