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I-have-five-envelopes-numbered-3-4-5-6-7-all-hidden-in-a-box-i-picked-an-envelope-If-its-prime-then-i-get-the-square-of-that-number-in-Naira-Otherwise-without-replacement-i-picked-another-env




Question Number 7168 by Tawakalitu. last updated on 14/Aug/16
I have five envelopes numbered 3,4,5,6,7 all hidden in a  box, i picked an envelope .  If its prime then i get the   square of that number in Naira. Otherwise (without   replacement) i picked another envelope and then get the  sum of the squares of the two numbers picked (in Naira)  what is the chance of me getting  N25  ?
Ihavefiveenvelopesnumbered3,4,5,6,7allhiddeninabox,ipickedanenvelope.IfitsprimethenigetthesquareofthatnumberinNaira.Otherwise(withoutreplacement)ipickedanotherenvelopeandthengetthesumofthesquaresofthetwonumberspicked(inNaira)whatisthechanceofmegettingN25?
Commented by Tawakalitu. last updated on 14/Aug/16
Yes correct ..... Thank you so much.
Yescorrect..Thankyousomuch.
Commented by Rasheed Soomro last updated on 14/Aug/16
I can get N25  only in the following two cases:  (i) If I picked 5   [∵  5^2 =25]  (ii) I f  I picked 4 and 3 in succession[∵ 4^2 +3^2 =25]  In case (i) the chance of getting 5 is  (1/5)    In case (ii) picking 4 has chance (1/5) and after  picking 4, picking 3 has (1/4) probablity.  Therefore picking 4 and 3 in succession has  probablity (1/5)×(1/4)=(1/(20))    Probablity of (picking 5) or  (4 and 3 in succession)  will be (1/5)+(1/(20))=((4+1)/(20))=(5/(20))=(1/4)???
IcangetN25onlyinthefollowingtwocases:(i)IfIpicked5[52=25](ii)IfIpicked4and3insuccession[42+32=25]Incase(i)thechanceofgetting5is15Incase(ii)picking4haschance15andafterpicking4,picking3has14probablity.Thereforepicking4and3insuccessionhasprobablity15×14=120Probablityof(picking5)or(4and3insuccession)willbe15+120=4+120=520=14???

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