Twenty meters of wire is available for fencing off a flower-bed

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 Multiple Choice QuestionsMultiple Choice Questions

131.

The x-coordinate of the incentre of the triangle that has the coordinates of mid points of its sides as (0, 1) (1, 1) and (1, 0) is

  • 2 plus square root of 2
  • 2 minus square root of 2
  • 1 plus square root of 2
  • 1 plus square root of 2
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132.

Twenty meters of wire is available for fencing off a flower-bed in the form of a circular sector.Then the maximum area (in sq. m) of the flower-bed, is

  • 30

  • 12.5

  • 10

  • 10


D.

10

Total length = r + r + rθ = 20

straight theta space equals space fraction numerator 20 space minus 2 straight r over denominator straight r end fraction
Area space space equals space 1 half straight r squared straight theta space equals 1 half straight r squared open parentheses fraction numerator 20 minus 2 straight r over denominator straight r end fraction close parentheses
straight A space equals space 10 straight r minus straight r squared
dA over dr space equals space 0
10 minus 2 straight r space equals space 0
straight r space equals 5
straight A space equals space 50 minus 25 space equals space 25

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133.

The projections of a vector on the three coordinate axis are 6, - 3, 2 respectively. The direction cosines of the vector are

  •  6, –3, 2 

  • 6/5, -3/5, 2/5

  • 6/7, -3/7, 2/7

  • 6/7, -3/7, 2/7

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134.

A triangular park is enclosed on two sides by a fence and on the third side by a straight river bank. The two sides having fence are of same length x. The maximum area enclosed by the park is

  • 3x2/2

  • x3/8

  • x2/2

  • x2/2

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135.

If (a, a2 ) falls inside the angle made by the lines y =x/2, x >0 and y = 3x, x > 0, then a belongs to

  • (0,1/2)

  • (3, ∞)

  • (1/2, 3)

  • (1/2, 3)

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136.

Let A(2,- 3) and B(- 2,1) be two angular points of AABC. If the centroid of the triangle moves on the line 2x + 3y = 1, then the locus of the angular point C is given by

  • 2x + 3y = 9

  • 2x - 3y = 9

  • 3x + 2y = 5

  • 3x + 2y = 3


137.

A particle starts moving from rest from a fixed point in a fixed direction. The distance s from the fixed point at a time t is given by s = t2 + at - b + 17, where a and b are real numbers. If the particle comes to rest after 5 s at a distance of s = 25 units from the fixed point, then values of a and b are, respectively

  • 10, - 33

  • - 10, - 33

  • - 8, 33

  • - 10, 33


138.

If a, band c are in AP, then the straight line ax + 2by + c = 0 will always pass through a fixed point whose coordinates are

  • (1, - 1)

  • (- 1, 1)

  • (1, - 2)

  • (- 2, 1)


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139.

The number of diagonals in a regular polygon of 100 sides is

  • 4950

  • 4850

  • 4750

  • 4650


140.

Let p, q and r be the altitudes of a triangle with area S and perimeter 2 t. Then, the value of 1p + 1q + 1r is

  • St

  • tS

  • S2t

  • 2St


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