Step-by-step explanation:
let me see, if I understand this right.
7 pairs of green socks = 14 green socks.
6 pairs of white socks = 12 white socks.
5 pairs of red socks = 10 red socks.
4 pairs of blue socks = 8 blue socks.
in total : 44 socks (or 22 pairs).
the person is pulling socks always 2 at a time. but each sock can be any color.
or are the pairs still connected, and each draw pulls a pair of equal socks ?
and then the question also really is, what is meant by 4 pairs have the same color ? that i find 4 groups of 2 socks each with the save color inside the group (making them pairs), or truly 4 pairs with the same color (e.g. 4 red pairs, or 4 green pairs) ?
if the pairs are still connected, only the second question makes sense.
the worst that can happen in that scenario is drawing
3 pairs of blue socks.
3 pairs of red socks.
3 pairs of white socks.
3 pairs of green socks.
this now like in Baseball : the bases are loaded. any additional runner will cause a score.
because any additional draw must complete one of the groups of 4 pairs.
so, latest after the 4×3 = 12 draws, we get a 13th draw. that gives us 4 equally colored pairs of socks for sure.
so, we need 13 draws.
if each sock is in there individually, and we still want to have 4 pairs of socks all with the same color, then it starts similarly :
the socks get pulled 2 by 2 but that means each drawn pair can have different colors of the individual socks.
in the worst case after drawing 24 socks (12 groups of 2 socks), we have the same situation as in the previous case.
but now, pulling 2 more socks does not guarantee a full set of 4 pairs. we could get 2 different socks that add only half a pair to 2 color groups.
the same with the next pulled group of 2. they fill up the other 2 color groups with half-pairs.
but now the base are loaded. by pulling the next (3rd) additional group of 4, we complete at least one color group with 4 full pairs.
so, we need 12 + 3 = 15 draws to make absolutely sure.
now, if we have individual socks, and want to get 4 pairs of socks that have just the same color inside their pair, we need to think a little bit differently.
after 2 draws (4 socks) we have in the worst case 4 individual socks with different colors.
after the next 2 draws we can be already lucky, but in the worst case we are not but have now either 2.5 full pairs of one color and 3 individual socks, or 2 full pairs in one color, 1 full pair in a second color, and 2 individual socks, or 1.5 pairs in one color, 2×1 full pairs in 2 other colors, and 1 individual sock.
with the next draw in the worst case we could only extend the second case and get 2.5 pairs in one color, 1.5 pairs in the second color and still 2 individual socks.
but now the bases are loaded, and the next draw of 2 socks guarantees that we have 4 real pairs of socks (either 3 and 1 and still 2 individual socks, or 3 and 2 pairs and 2 individual socks, or 2 and 2×1 and wherever the second sock goes, it does not matter, or any other combination where at least one of the individual socks have been combined to a pair.
so, we need
2+2+1+1 = 6 draws.
