Let R = No. Red, B = No. Blue, W = No. White , G = No. Green and T = Total
And we have that
R / T * (R -1)/[T - 1] * (R - 2)/[T- 2] * (R -3)/ [T - 3] =
B/T * ( R ) /[ T - 1] * (R - 1) / [T - 2] * (R - 2) / [ T --3] ⇒
R * (R -1) * (R - 2) * (R - 3) = B * R * (R - 1) * (R -2) ⇒
(R - 3) = B
And
R / T * (R -1)/[T - 1] * (R - 2)/[T- 2] * (R -3)/ [T - 3] =
W/T * (R -3)/ [T -1] * R/ [ T - 2] * (R -1) / [T - 3] ⇒
R (R -1) (R - 2) ( R - 3) = W * (R -3) (R) ( R -1) ⇒
(R - 2) = W
And
R / T * (R -1)/[T - 1] * (R - 2)/[T- 2] * (R -3)/ [T - 3] =
R /T * (R -3)/[ T - 1] * (R -2) / [ T - 2] * G / [T - 3] ⇒
R (R -1) (R - 2) (R -3) = R (R -3) (R -2) G ⇒
(R -1) = G
So
R = R
B = R - 3
W = R - 2
G = R - 1
Let the number of blue = 1
Let the number of white = 2
Let the number of green = 3
Let the number of red = 4
Probability of drawing 4 red =
[ 4 * 3 * 2 * 1 ] / [10 * 9 * 8 * 7 ] = 24 / 5040
Probability of one blue, three reds =
[ 1 * 4 * 3 * 2] / [ 10 * 9 * 8 * 7] = 24 / 5040
Probability of one white, one blue, two reds =
[ 2 * 1 * 4 * 3 ] / [ 10 * 9 * 8 * 7] = 24 / 5040
Probability of one of each color =
[1 * 2 * 3 * 4 ] / [10 * 9 * 8 * 7 ] = 24 / 5040
So...the minimum number is 10