Heron’s Formula – Find the area of a triangle two sides of which are 18cm and 10cm and the perimeter is 42 cm – MBS Classes

Course Content

Live Class

Live

0/1

🔴 LIVE CLASS — Class 9

Important Problems – Class 9

Ace your Class 9 Maths exams with a focused set of the most important problems! These cover all key chapters and concepts, designed to strengthen your understanding and boost your confidence. 📌 Highlights: Covers NCERT, exam-focused problems Step-by-step solutions for clarity Tricks to solve quickly and accurately Perfect for revision and last-minute preparation!

0/141

Important Problems – Polynomial – Part 01

Important Problems – Polynomial – Part 02

Important Problems – Quadrilateral – Quadrilateral Theorem 8.1 A diagonal of a parallelogram divides it into two congruent triangles.

Important Problems – Quadrilateral – Show that the diagonals of a rhombus are perpendicular to each other

Important Problems – Quadrilateral – If the diagonals of a parallelogram are equal, then show that it is a rectangle

Important Problems – Quadrilateral – Diagonal AC of a parallelogram ABCD bisects A. Show that it bisects c also ABCD is a rhombus

Important Problems – Quadrilateral – ABCD is a rectangle in which diagonal AC bisects angle A as well as angle C Show that ABCD is a square

Important Problems – Quadrilateral – In parallelogram ABCD, two points P and Q are taken on diagonal BD such that DP = BQ

Important Problems – Quadrilateral – ABCD is a parallelogram and AP and CQ are perpendiculars from vertices A and C on diagonal BD (see figure). Show that

Important Problems – Quadrilateral – In Δ ABC and Δ DEF, AB = DE, AB DE, BC = EF and BC EF. Vertices A, B and C are joined to vertices D, E and F respectively (see Fig. 8.22). Show that

Important Problems – Quadrilateral – ABCD is a trapezium in which AB is parallel to CD and AD = BC Show that

Important Problems – Quadrilateral – ABCD is a quadrilateral in which P, Q, R and S are midpoints of the sides AB, BC, CD and DA see Fig 8.29 AC is a diagonal Show that

Important Problems – Quadrilateral – ABCD is a rhombus and P, Q, R and S are the mid-points of the sides AB, BC, CD and DA respectively. Show that the quadrilateral PQRS is a rectangle.

Important Problems – Quadrilateral – ABCD is a rectangle and P, Q, R and S are mid-points of the sides AB, BC, CD and DA respectively. Show that the quadrilateral PQRS is a rhombus

Important Problems – Quadrilateral – ABCD is a trapezium in which AB DC, BD is a diagonal and E is the mid-point of AD. A line is drawn through E parallel to AB intersecting BC at F. Show that F is the mid-point of BC.

Important Problems – Quadrilateral – In a parallelogram ABCD, E and F are the mid-points of sides AB and CD respectively. Show that the line segments AF and EC trisect the diagonal BD.

Important Problems – Quadrilateral – Show that the line segments joining the mid-points of the opposite sides of a quadrilateral bisect each other

Important Problems – Quadrilateral – ABC is a triangle right angled at C. A line through the mid-point M of hypotenuse AB and parallel to BC intersects AC at D. Show that (i) D is the mid-point of AC (ii) MD ⊥ AC (iii) CM = MA = 1 / 2 AB

Important Problems – Surface Area & Volume – Diameter of the base of a cone is 10.5 cm and its slant height is 10 cm. Find its curved surface area

Important Problems – Surface Area & Volume – A conical tent is 10 m high and the radius of its base is 24 m Find slant height of the tent cost of the canvas required to make the tent if the cost of 1 m2 canvas is Rs 70

Important Problems – Circles – Equal chords of a circle subtend equal angles at the center.

Important Problems – Circles – Recall that two circles are congruent if they have the same radii. Prove that equal chords of congruent circles subtend equal angles at their centres.

Important Problems – Circles – Prove that if chords of congruent circles subtend equal angles at their centres then the chords are equal

Important Problems – Circles – Two circles of radii 5 cm and 3 cm intersect at two points and the distance between their centres is 4 cm Find the length of the common chord

Important Problems – Circles – If two equal chords of a circle intersect within the circle, prove that the segments of one chord are equal to corresponding segments of the other chord.

Important Problems – Circles – If two equal chords of a circle intersect within the circle prove that the line joining the point of intersection to the centre makes equal angles with the chords

Important Problems – Circles – If a line intersects two concentric circles (circles with the same centre) with centre O at A, B, C and D, prove that AB = CD (see Fig. 10.25).

Important Problems – Circles – Three girls Reshma, Salma and Mandip are playing a game by standing on a circle of radius 5m drawn in a park. Reshma throws a ball to Salma, Salma to Mandip, Mandip to Reshma. If the distance between Reshma and Salma

Important Problems – Circles – A circular park of radius 20m is situated in a colony. Three boys Ankur, Syed and David are sitting at equal distance on its boundary each having a toy telephone in his hands to talk each other. Find the length of

Important Problems – Circles – In Fig. 10.36, A,B and C are three points on a circle with centre O such that ∠ BOC = 30° and ∠ AOB = 60°. If D is a point on the circle other than the arc ABC, find ∠ADC.

Important Problems – Circles – A chord of a circle is equal to the radius of the circle. Find the angle subtended by the chord at a point on the minor arc and also at a point on the major arc

Important Problems – Circles – In Fig. 10.37, ∠ PQR = 100°, where P, Q and R are points on a circle with centre O. Find ∠ OPR

Important Problems – Circles – In Fig 10 38, ∠ ABC = 69°, ∠ ACB = 31°, find ∠ BDC

Important Problems – Circles – In Fig. 10.39, A, B, C and D are four points on a circle. AC and BD intersect at a point E such that ∠ BEC = 130° and ∠ ECD = 20°. Find ∠ BAC

Important Problems – Circles – ABCD is a cyclic quadrilateral whose diagonals intersect at a point E. If ∠ DBC = 70°, ∠ BAC is 30°, find ∠ BCD. Further, if AB = BC, find ∠ ECD.

Important Problems – Circles – If diagonals of a cyclic quadrilateral are diameters of the circle through the vertices of the quadrilateral, prove that it is a rectangle.

Important Problems – Circles – If the non parallel sides of a trapezium are equal, prove that it is cyclic.

Important Problems – Circles – In Fig A, B, C and D are four points on a such that ∠ BEC = 130° and ∠ ECD = 20°. Find ∠ BAC

Important Problems – Circles – If circles are drawn taking two sides of a triangle as diameters, prove that the point of intersection of these circles lie on the third side

Important Problems – Circles – ABC and ADC are two right triangles with common hypotenuse AC Prove that ∠ CAD = ∠ CBD

Important Problems – Circles – Prove that a cyclic parallelogram is a rectangle

Heron’s Formula – A traffic signal board, indicating ‘SCHOOL AHEAD’, is an equilateral triangle with side ‘a’. Find the area of the signal board, using Heron’s formula. If its perimeter is 180 cm, what will be the area of the signal board?

Heron’s Formula – The triangular side walls of a flyover have been used for advertisements. The sides of the walls are 122 m, 22 m and 120 m (see Fig. 10.6). The advertisements yield an earning of Rs. 5000 per m2 per year.

Heron’s Formula – There is a slide in a park. One of its side walls has been painted in some colour with a message “KEEP THE PARK GREEN AND CLEAN” (see Fig. 12.10 ). If the sides of the wall are 15 m, 11 m and 6 m, find the area painted in colour.

Heron’s Formula – Find the area of a triangle two sides of which are 18cm and 10cm and the perimeter is 42 cm

Heron’s Formula – Sides of a triangle are in the ratio of 12:17:25 and its perimeter is 540 cm Find its area

Heron’s Formula – An isosceles triangle has perimeter 30 cm and each of the equal sides is 12 cm. Find the area of the triangle

Number System Ex 1.1

Number System Ex 1.2

Number System Ex 1.3 – Problems Solution 1 & 2

Number System Ex 1.3 – Problem Solution 3

Number System Ex 1.3 – Problem Solution 4

Number System Ex 1.3 – Problem Solution 5

Number System Ex 1.3 – Problem Solution 6

Number System Ex 1.3 – Problem Solution 7

Number System Ex 1.3 – Problem Solution 8

Number System Ex 1.3 – Problem Solution 9

Number System Ex 1.4 – Problem Solution 1

Number System Ex 1.4 – Problem Solution 2

Number System Ex 1.4 – Problem Solution 5

Number System Ex 1.5 – Problem Solution 1

Number System Ex 1.5 – Problem Solution 2

Number System Ex 1.5 – Problem Solution 3

Polynomials Ex 2.1 – Problem Solution 1

Polynomials Ex 2.1 – Problem Solution 2

Polynomials Ex 2.1 – Problem Solution 3

Polynomials Ex 2.1 – Problem Solution 4

Polynomials Ex 2.1 – Problem Solution 5

Polynomials Ex 2.2 – Problems Solution 1

Polynomials Ex 2.2 – Problems Solution 2

Polynomials Ex 2.2 – Problems Solution 3

Polynomials Ex 2.2 – Problems Solution 4

Polynomials Ex 2.3 – Problem Solution 1 (i)

Polynomials Ex 2.3 – Problem Solution 1 (ii)

Polynomials Ex 2.3 – Problem Solution 1 (iii)

Polynomials Ex 2.3 – Problem Solution 1 (iv)

Polynomials Ex 2.3 – Problem Solution 1 (v)

Polynomials Ex 2.3 – Problem Solution 2

Polynomials Ex 2.3 – Problem Solution 3

Polynomials Ex 2.4 – Problem Solution 1 (i)

Polynomials Ex 2.4 – Problem Solution 1 (ii)

Polynomials Ex 2.4 – Problem Solution 1 (iii)

Polynomials Ex 2.4 – Problem Solution 1 (iv)

Polynomials Ex 2.4 – Problem Solution 2 (i)

Polynomials Ex 2.4 – Problem Solution 2 (iii)

Polynomials Ex 2.4 – Problem Solution 3 (i)

Polynomials Ex 2.4 – Problem Solution 3 (ii)

Polynomials Ex 2.4 – Problem Solution 3 (iii)

Polynomials Ex 2.4 – Problem Solution 3 (iv)

Polynomials Ex 2.4 – Problem Solution 4 (i)

Polynomials Ex 2.4 – Problem Solution 4 (ii)

Polynomials Ex 2.4 – Problem Solution 4 (iii)

Polynomials Ex 2.4 – Problem Solution 4 (iv)

Polynomials Ex 2.4 – Problem Solution 5 (i) (By Simple Method)

Polynomials Ex 2.4 – Problem Solution 5 (i) (By Long Division Method)

Polynomials Ex 2.4 – Problem Solution 5 (ii)

Polynomials Ex 2.4 – Problem Solution 5 (iii)

Polynomials Ex 2.4 – Problem Solution 5 (iv)

Polynomials Ex 2.5 – Problem Solution 1 (i)

Polynomials Ex 2.5 – Problem Solution 1 (ii)

Polynomials Ex 2.5 – Problem Solution 1 (iii)

Polynomials Ex 2.5 – Problem Solution 1 (iv)

Polynomials Ex 2.5 – Problem Solution 1 (v)

Polynomials Ex 2.5 – Problem Solution 2 (i)

Polynomials Ex 2.5 – Problem Solution 2 (ii)

Polynomials Ex 2.5 – Problem Solution 2 (iii)

Polynomials Ex 2.5 – Problem Solution 3 (i)

Polynomials Ex 2.5 – Problem Solution 3 (ii)

Polynomials Ex 2.5 – Problem Solution 3 (iii)

Polynomials Ex 2.5 – Problem Solution 4 (i)

Polynomials Ex 2.5 – Problem Solution 4 (ii)

Polynomials Ex 2.5 – Problem Solution 4 (iii)

Polynomials Ex 2.5 – Problem Solution 4 (iv)

Polynomials Ex 2.5 – Problem Solution 4 (v)

Polynomials Ex 2.5 – Problem Solution 4 (vi)

Polynomials Ex 2.5 – Problem Solution 5 (i)

Polynomials Ex 2.5 – Problem Solution 5 (ii)

Polynomials Ex 2.5 – Problem Solution 6 (i)

Polynomials Ex 2.5 – Problem Solution 6 (ii)

Polynomials Ex 2.5 – Problem Solution 6 (iii)

Polynomials Ex 2.5 – Problem Solution 6 (iv)

Polynomials Ex 2.5 – Problem Solution 7 (i)

Polynomials Ex 2.5 – Problem Solution 7 (ii)

Polynomials Ex 2.5 – Problem Solution 7 (iii)

Polynomials Ex 2.5 – Problem Solution 8 (i)

Polynomials Ex 2.5 – Problem Solution 8 (ii)

Polynomials Ex 2.5 – Problem Solution 8 (iii)

Polynomials Ex 2.5 – Problem Solution 8 (iv)

Polynomials Ex 2.5 – Problem Solution 8 (v)

Polynomials Ex 2.5 – Problem Solution 9 (i)

Polynomials Ex 2.5 – Problem Solution 9 (ii)

Polynomials Ex 2.5 – Problem Solution 10 (i)

Polynomials Ex 2.5 – Problem Solution 10 (ii)

Polynomials Ex 2.5 – Problem Solution 12

Polynomials Ex 2.5 – Problem Solution 13

Polynomials Ex 2.5 – Problem Solution 14 (i)

Polynomials Ex 2.5 – Problem Solution 14 (ii)

Polynomials Ex 2.5 – Problem Solution 15 (i)

Polynomials Ex 2.5 – Problem Solution 15 (ii)

Polynomials Ex 2.5 – Problem Solution 16 (i)

Polynomials Ex 2.5 – Problem Solution 16 (ii)

Coordinate Geometry

0/1

Coordinate Geometry Ex 3.2 – All Solutions in one

Linear Equation in two variables

0/2

Linear Equation in two variables Ex 4.1 – All Problems in one

Linear Equation in two variables Ex 4.2 – All Problems in One

Lines and Angles

0/5

Lines and Angles Ex 6.1 – Problem Solution 1

Lines and Angles Ex 6.1 – Problem Solution 2

Lines and Angles Ex 6.1 – Problem Solution 3

Lines and Angles Ex 6.1 – Problem Solution 4

Lines and Angles Ex 6.1 – Problem Solution 5

Best Free Videos for Class 9 Maths – Master Concepts with Ease!

Find the area of a triangle two sides of which are 18cm and 10cm and the perimeter is 42 cm