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A picnic party of 4 persons is to be selected from 8 engineers and 3 doctors so as to include at least one doctor.The possible number of ways are
1)168
2)84
3)8
4)260

sol> 

 

if   1 doctor  and 3 engineers 

8c3=56
3c1=3
56*3=168


if 2 doctor and 1 engineer

2d n 2e
3c2=3 8c2=28
28*3=84

if 3 doctor and 1 engineer

3d and 1e
3c3=1  8c1=8
8*1=8

so sum is=168+84+8=260