NCERT Mathematics Class 9 Exemplar Ch 12 Heron's Formula Part 5

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Exercise 12.4

Q.1. How much paper of each shade is needed to make a kite given in Fig. 12.4, in which ABCD is a square with diagonal 44 cm.

ABCD is a square with diagonal 44 cm

ABCD is a Square with Diagonal 44 Cm

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Answer: Yellow: ; Red : ; Green :

Q.2. The perimeter of a triangle is One side of a triangle is 4 cm longer than the smaller side and the third side is 6 cm less than twice the smaller side. Find the area of the triangle.


Q.3. The area of a trapezium is and the height is Find the lengths of its two parallel sides if one side is 4 cm greater than the other.


Q.4. A rectangular plot is given for constructing a house, having a measurement of long and in the front. According to the laws, a minimum of 3 m, wide space should be left in the front and back each and 2 m wide space on each of other sides. Find the largest area where house can be constructed.


Q.5. A field is in the shape of a trapezium having parallel sides and These sides meet the third side at right angles. The length of the fourth side is If it costs Rs 4 to plough of the field, find the total cost of ploughing the field.

Answer: Rs 19200

ABC has sides AB = 7.5 cm,

ABC Has Sides AB = 7.5 Cm

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Q.6. In Fig. 12.5, ∆ ABC has sides , and On base BC a parallelogram DBCE of same area as that of ∆ ABC is constructed. Find the height DF of the parallelogram.