Question 1120190
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He can choose either<br>
(1) chemistry part 1 and any 2 of the other 7 books: C(1,1)*C(7,2) = 1*21 = 21<br>
or<br>
(2) not chemistry part 1, and therefore not chemistry part 2, and any 3 of the other 6 books: C(6,3) = 20<br>
The total number of ways he can choose 3 books is 21+20 = 41.