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A student has a collection of 9 cds, 5 of the CDs are classical, 2 are JAZZ and 2 are ROCKS.
If he selects 6 CDs from his collection, find the number of ways he can make his selection
if it must contain at least 4 CLASSICAL.
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According to the problem, the student can select 4 classical CDs from 5 classical CDs
and to complete this selection by 2 (two) non-classical CDs from 2+2 = 4 non-classical CDs.
OR, alternatively, the student can select 5 classical CDs from 5 classical CDs
and to complete it by 1 (one) non-classical CDs from 4 non-classical CDs.
In all, there are + = 5*6 + 1*4 = 30 + 4 = 34 such possible selections. ANSWER
Solved.