Santosa, the question says she *may* choose to go barefoot. Hence there is an option, either she can wear one of her ten pairs of shoes or none of them, thus giving 11 options in all. Had it said she *will* go barefoot, then there would be only one option!
Avinash, suppose you got the first rank in History. Would that prevent you from also getting the first in Geography? The thing is that in this question, both “first ranks” can go to the same person. So whoever gets the top in Geography, there are ten people (including that person) who could get the first in History and hence 10 * 10. This is the basis on which most “repetition allowed” questions are based in fact.
Hello sir,In last question if we have question like 4 multiple questions with 5 choices each .In how many ways questions could be done if one must do at least 2 questions?
No we would also need to check which questions are answered in each case. So it would be 1 (0 questions) + 4C1*5 (1 question) + 4C2*25 (2 questions)and so on. Which would yield the same answer eventually, just more painfully!
in question 2,it was written barefoot, so with no pair of shoes i.e.1
how is this 11??
By santosa on March 26, 2013 at 2:48 PM
Santosa, the question says she *may* choose to go barefoot. Hence there is an option, either she can wear one of her ten pairs of shoes or none of them, thus giving 11 options in all. Had it said she *will* go barefoot, then there would be only one option!
J
By catcracker on March 26, 2013 at 2:56 PM
ohh thank you…
btw ur articles r vry good & informative.
keep up d gd work…:)
By santosa on March 27, 2013 at 6:07 PM
the first rank in geography and first rank in history question, i didn’t understand. could you please elaborate?
By avinash on June 6, 2013 at 7:32 PM
Avinash, suppose you got the first rank in History. Would that prevent you from also getting the first in Geography? The thing is that in this question, both “first ranks” can go to the same person. So whoever gets the top in Geography, there are ten people (including that person) who could get the first in History and hence 10 * 10. This is the basis on which most “repetition allowed” questions are based in fact.
regards
J
By catcracker on June 6, 2013 at 9:19 PM
Hello sir,In last question if we have question like 4 multiple questions with 5 choices each .In how many ways questions could be done if one must do at least 2 questions?
By Pranita on July 23, 2014 at 10:52 PM
Pranita, then we would remove the cases where 0 or 1 question was answered. So 6^4 – 1 – 5*4 = 1296 – 21 = 1275 ways.
regards
J
By catcracker on July 24, 2014 at 10:35 AM
sir, shouldn’t it be 5^4 – 1 – 5*4 = because attempting all questions in 5^4 ways?
By seema on June 23, 2016 at 9:59 AM
No Seema, because each question still has the option of “not attempted” so 6 possibilities.
By catcracker on June 23, 2016 at 11:51 AM
but it says, “at least 2 needs to be done” and in 6^4, if all were left unattempted, then?
By seema on June 24, 2016 at 8:01 AM
That’s the first ( – 1) in the answer.
By catcracker on June 24, 2016 at 12:17 PM
Why not all persons get first rank? The question doesn’t say only one should get first rank.
By Jayavignesh Ravichandran on September 12, 2014 at 2:06 PM
Long answer – when the question says “the first rank” then it is understood that there is only one first rank. Similarly for “the second rank.
Short answer “Bhavnaon ko samjho” 😛
regards
J
By catcracker on September 12, 2014 at 9:42 PM
Could you tell your short answer in English.I don’t know Hindi
By jayavignesh Ravichandran on September 13, 2014 at 10:47 AM
“Understand the intentions”. There’s this site called Google which would help in such cases, you know…try it sometime.
regards
J
By catcracker on September 13, 2014 at 11:33 AM
Sir, in the last question, can;t it be she attempts 0 ques or 1 ques or 2 ques and so on. 5(for 1ques)+ 25(for 2) +125+625
By Rohit Gupta on August 30, 2019 at 4:56 PM
No we would also need to check which questions are answered in each case. So it would be 1 (0 questions) + 4C1*5 (1 question) + 4C2*25 (2 questions)and so on. Which would yield the same answer eventually, just more painfully!
regards
J
By catcracker on August 31, 2019 at 10:55 AM
Glad I found your blog, will be revising all concepts from here in the remaining days 😀
By Chetna on November 17, 2020 at 9:58 PM