Area and Perimeter


  1. The adjacent sides of parallelogram are 6 cm and 4 cm and the angle between then is 30°. The area of the parallelogram is ?









  1. View Hint View Answer Discuss in Forum

    AB = 6 cm ; AD = 4 cm and ∠ BAD = 30°
    Area of parallelogram ABCD = AB x AD x sin 30°

    Correct Option: A

    AB = 6 cm ; AD = 4 cm and ∠ BAD = 30°
    Area of parallelogram ABCD = AB x AD x sin 30°
    = 6 x 4 x sin 30° = 12 cm2


  1. A triangle with three equal sides has its area equal to 3√3 sq cm . Find its perimeter .









  1. View Hint View Answer Discuss in Forum

    area = √3a2/4
    where a = side.

    Required perimeter = 3a

    Correct Option: A

    According to the question,
    3a2/4 = 3√3 [ side = a, and area = √3a2/4]
    ⇒ a2/4 = 3
    ⇒ a2 = 3 x 4
    ∴ a = 2√3

    ∴ Required perimeter = 3a
    =3 x 2√3
    = 6√3 cm



  1. The three sides of a triangle are 15, 25 and x units. Which one of the following is correct?









  1. View Hint View Answer Discuss in Forum

    In a triangle
    1. Sum of two sides is always greater than 3rd side
    2. Difference of two sides is always less than 3rd side

    Correct Option: A

    In a triangle
    Sum of two sides is always greater than 3rd side
    i.e., x < 25 + 15 = 40 .....(i)

    Difference of two sides is always less than 3rd side
    i.e., 25 - 15 = 10 < x ...(ii)

    From Eqs. (i) and (ii) , we get
    10 < x < 40


  1. The lengths of three line segments (in cm) are given in each of the four cases. Which one of the following cases is not suitable to be the three sides of a triangle?









  1. View Hint View Answer Discuss in Forum

    We know that in any triangle
    "the sum of two sides is always greater than its third side" and
    "the difference of two sides is always less than its third side".
    (i) 2 + 3 is not greater than 5
    (ii) |5 - 2| not less than 3

    Correct Option: B

    We know that in any triangle
    "the sum of two sides is always greater than its third side" and
    "the difference of two sides is always less than its third side".
    (i) 2 + 3 is not greater than 5
    (ii) |5 - 2| not less than 3



  1. The sides of a triangle area in the ratio of 1/3 : 1/4 : 1/5 and its perimeter is 94 cm.
    Find the length of the smallest side of the triangle .









  1. View Hint View Answer Discuss in Forum

    Given ratio = 1/3 : 1/4 : 1/5 = 20 : 15 : 12
    Let length of the sides be 20k, 15k and 12k.

    Then, according to the question,
    20k + 15k + 12k = 94

    Correct Option: C

    Given ratio = 1/3 : 1/4 : 1/5 = 20 : 15 : 12
    Let length of the sides be 20k, 15k and 12k.

    Then, according to the question,
    20k + 15k + 12k = 94
    ⇒ 47k = 94
    ∴ k = 94/47 = 2

    Smallest side = 12k = 12 x 2 = 24 cm