Subject

Mathematics

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsLong Answer Type

31.

Using integration, find the area of the region enclosed between the two circles:
straight x squared plus straight y squared space equals space 4 space and space left parenthesis straight x minus 2 right parenthesis squared plus straight y squared space equals space 4.

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32.

Show that the differential equation 2 ye to the power of straight x divided by straight y end exponent dx plus left parenthesis straight y minus 2 straight x space straight e to the power of straight x divided by straight y end exponent right parenthesis space dy space equals space 0 is homogeneous. Find the particular solution of this differential equation, given that x = 0 when y = 1.

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33.

Find the vector equation of the plane passing through three points with position vectors straight i with hat on top plus straight j with hat on top minus 2 straight k with hat on top comma space 2 straight i with hat on top minus straight j with hat on top plus straight k with hat on top space and space straight i with hat on top plus 2 straight j with hat on top plus straight k with hat on top. Also, find the coordinates of the point of intersection of this plane and the line straight r with rightwards arrow on top space equals 3 straight i with hat on top minus straight j with hat on top minus straight k with hat on top plus straight lambda open parentheses 2 straight i with hat on top minus 2 straight j with hat on top plus straight k with hat on top close parentheses.

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34.

A cooperative society of farmers has 50 hectares of land to grow two crops A and B. The profits from crops A and B per hectare are estimated as Rs 10,500 and Rs 9,000 respectively. To control weeds, a liquid herbicide has to be used for crops A and B at the rate of 20 litres and 10 litres per hectare, respectively. Further not more than 800 litres of herbicide should be used in order to protect fish and wildlife using a pond which collects drainage from this land. Keeping in mind that the protection of fish and other wildlife is more important than earning profit, how much land should be allocated to each crop so as to maximize the total profit? Form an LPP from the above and solve it graphically. Do you agree with the message that the protection of wildlife is utmost necessary to preserve the balance in environment?

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35.

Assume that the chances of a patient having a heart attack is 40%. Assuming that a meditation and yoga course reduces the risk of heart attack by 30% and prescription of certain drug reduces its chance by 25%. At a time a patient can choose any one of the two options with equal probabilities. It is given that after going through one of the two options, the patient selected at random suffers a heart attack. Find the probability that the patient followed a course of meditation


Let A, E1, and E2, respectively denote the events that a person has a heart attack, the selected person followed the course of yoga and meditation, and the person adopted the drug prescription.
therefore space space straight P left parenthesis straight A right parenthesis space equals space 0.40
straight P left parenthesis straight E subscript 1 right parenthesis thin space equals space straight P left parenthesis straight E subscript 2 right parenthesis space equals space 1 half
straight P left parenthesis straight A vertical line straight E subscript 1 right parenthesis space equals space 0.40 space cross times space 0.70 space equals space 0.28
straight P left parenthesis straight A vertical line straight E subscript 2 right parenthesis space equals 0.40 space cross times space 0.75 space equals space 0.30

Probability that the patient suffering a heart attack followed a course of meditation and yoga = straight P left parenthesis straight E subscript 1 vertical line straight A right parenthesis
equals space fraction numerator straight P left parenthesis straight E subscript 1 right parenthesis thin space straight P left parenthesis straight A vertical line straight E subscript 1 right parenthesis over denominator straight P left parenthesis straight E subscript 1 right parenthesis thin space straight P left parenthesis straight A vertical line straight E subscript 1 right parenthesis plus straight P left parenthesis straight E subscript 2 right parenthesis thin space straight P left parenthesis straight A vertical line straight E subscript 2 right parenthesis end fraction
equals fraction numerator begin display style 1 half end style cross times 0.28 over denominator begin display style 1 half end style cross times 0.28 plus begin display style 1 half end style cross times 0.30 end fraction
equals fraction numerator 28 over denominator 28 plus 30 end fraction
equals 28 over 58
equals 14 over 29
Now, calculate straight P left parenthesis straight E subscript 2 vertical line straight A right parenthesis.
straight P left parenthesis straight E subscript 2 vertical line straight A right parenthesis space equals space fraction numerator straight P left parenthesis straight E subscript 2 right parenthesis thin space straight P left parenthesis straight A vertical line straight E subscript 2 right parenthesis over denominator straight P left parenthesis straight E subscript 1 right parenthesis thin space straight P left parenthesis straight A vertical line straight E subscript 1 right parenthesis plus straight P left parenthesis straight E subscript 2 right parenthesis space straight P left parenthesis straight A vertical line straight E subscript 2 right parenthesis end fraction
space space space space space space space space equals fraction numerator begin display style 1 half end style cross times 0.30 over denominator begin display style 1 half end style cross times 0.28 plus begin display style 1 half end style cross times 0.30 end fraction
space space space space space space space space space space space equals fraction numerator 30 over denominator 28 plus 30 end fraction
space space space space space space space space space space space space equals 30 over 58
space space space space space space space space space space space space equals 15 over 29
Since straight P left parenthesis straight E subscript 1 vertical line straight A right parenthesis space less than thin space straight P left parenthesis straight E subscript 2 vertical line straight A right parenthesis , the course of yoga and meditation is more beneficial for a patient. 


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