1rite sky try others [1]
55> ORIGIN is an interior point of an ellipse wose foci correspond to the complex numbers z1 and z2 .
Then the eccentricity of the ellipse is :
218> A die is thrown as long as necessary for one ace or six to turn up . Given that no ace turns at the first two throws , the probability that atleast three throws are necessary is
a>4/5 b>16/25 c>9/25 d>1/5
227> If there are 5 envelopes and 5 letters correspondingly , the probability that not all the letters are put in the correct envelope is
a> 1/120 b>119/120 c>59/120 d>27/40
please use derrangemtnt concept [1]
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7 Answers
1227> ans B.
there are 5! ways..of shuffling.. among that only one is correct.
so ans 119/120.
i dunno derrangement concept..
1218.
prob=1-prob of at most two throws necessary.
=1-((1/5)+(4/5)(1/5))
=16/25
1
THIS IS THE SOLUTION TO PROBLEM NO. 55
MAKE ME CLEAR IT
AM NOT GETTING THE MEANING OF IT
2a = PA + PB <<<??
2a IS LENGTH OF MAJOR AXIS.. AM NOT GETTING THEIR SOLUTION ATT ALL [2]
and also about postion of O am confused [2]