Question 1198950
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Toni has 10 identical blue socks, 14 identical green socks, and 4 identical red socks in a drawer. 
She removes socks from the drawer one at a time at random without looking. 
The least number of socks that Toni needs to pull out to be sure of having 4 pairs of the same colour is:
a) 8
b) 15
c) 16
d) 19
e) 22
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In the worst case scenario,  Toni will pull out 4 identical red socks,  7 identical blue socks and 7 identical green socks,

but still will not have 4 pairs of the same color.


Notice that         4 + 7 + 7 = 18   socks.


But then,  had Toni pull out anyone of remaining socks from the drawer,

this  19-th sock will create four pairs of identical socks,  either blue or green.


Therefore,  the least number of socks that Toni needs to pull out to be sure of having  4  pairs of the same color is  19.


Solved.