# How do we solve these permutation and combination questions? [closed]

Q1 In how many ways a panel of six doctors is selected from five surgeons and six physicians if condition is surgeons are more than physicians.
A 82 B 81 C 65 D 135

Q2 Find the no. of sequences in which seven players can throw a ball,so that the youngest player is not the last.
a 4000 b 2160 c 4320 d 5300

Q3 Ways of choosing two white squares in same row or column on an 8*8 chessboard-

a 12 b 96 c 48 d 60

## closed as off-topic by Nikunj, Graham Kemp, M. Vinay, user91500, hardmathMay 27 '16 at 13:13

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Nikunj, Graham Kemp, M. Vinay, user91500, hardmath
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• Have you tried anything ? – H. Potter May 27 '16 at 12:15
• Welcome to MSE. How far have you got? Q1 What are the possibilities for the number of surgeons? How many ways if you have 5 surgeons and 1 physician? – almagest May 27 '16 at 12:16

We have 4 or 5 surgeons among the 6 in the panel. Count these separately. The order does not matter, so we can pick the 4 surgeons in ${5 \choose 4}$ ways followed by ${6 \choose 2}$ ways to pick 2 physicians. Add this to ${5 \choose 5}{6 \choose 1}$ ways to pick all 5 surgeons and 1 physician. The correct answer is not among your answers, BTW, unless you modify a digit..