Class 9 Maths Ganita Manjari Chapter 6 Solutions (NCERT 2026–27) – Measuring Space: Perimeter and Area
These Class 9 Maths Ganita Manjari Chapter 6 solutions cover Measuring Space: Perimeter and Area from the new NCF-2023 textbook (2026–27). Every exercise is solved step by step — perimeters, areas, Heron’s formula, sectors and segments — so you can revise the whole chapter quickly.
Chapter 6 Overview
Chapter 6 of Ganita Manjari, Measuring Space: Perimeter and Area, develops the measurement of plane figures: perimeter and circumference, arc length and the perimeter of a sector, then area of rectangles, parallelograms, triangles (including Heron’s formula), trapeziums, rhombuses and kites, and finally the area of circles, sectors and segments. The Class 9 Maths Ganita Manjari Chapter 6 solutions below work through every exercise step by step. Unless stated otherwise, π = 22/7. Where a question depends on a textbook figure, the method and the determinable values are given.
Key Concepts
Perimeter is the total boundary length; for a circle it is the circumference = 2πr.
Arc length for a central angle θ = (θ/360) × 2πr; the sector perimeter = arc + 2r.
Area is the space enclosed, measured in square units.
Heron’s formula finds a triangle’s area from its three sides.
Sector = pie-slice region; segment = region between a chord and its arc (= sector − triangle).
All Formulas Used in This Chapter
Circle: circumference = 2πr; area = πr2. Semicircle perimeter = πr + 2r.
Arc length = (θ/360) × 2πr; sector area = (θ/360) × πr2.
Rectangle = l × b; parallelogram = base × height; triangle = ½ × base × height.
Heron: s = (a + b + c)/2, area = √(s(s − a)(s − b)(s − c)); equilateral side a = (√3/4)a2.
Trapezium = ½(a + b)h; rhombus / kite = ½ × d1 × d2.
Segment = sector − triangle.
Exercise Set 6.1 (π = 22/7)
1. The perimeter of a circle is 44 cm. What is its radius?
2. Calculate (to 3 significant figures) the circumference of a circle with: (i) radius 7 cm (ii) radius 10 cm (iii) radius 12 cm.
3. Calculate the length of the arc if: (i) radius 3.5 cm, central angle 60°; (ii) radius 6.3 m, central angle 120°.
4. Find the perimeter of a sector (curved part + two radii) of a circle of radius 14 cm and sector angle 75°.
5. Find the perimeters of the shapes in Fig. 6.14 (i)–(ix), taking the arcs to be quarter / half / three-quarter circles as appropriate.
6. If the diameter of a car tyre is 56 cm: (i) how far does the car travel in one revolution? (ii) how many revolutions for 10 km?
7. Find the total perimeter of all the petals in each flower (Fig. 6.15A, 6.15B).
8. The ratio of the perimeters of two circles is 5 : 4. What is the ratio of their radii?
Exercise Set 6.2
1. Find the area of triangle ADE in Fig. 6.31.
2. The parallel sides of a trapezium are 40 cm and 20 cm. Its non-parallel sides are equal, each 26 cm. Find the area.
3. Find the area of a triangle whose two sides are 8 cm and 11 cm and whose perimeter is 32 cm.
4. The sides of a triangular plot are in the ratio 3 : 5 : 7 and the perimeter is 300 m. Find its area.
5. One diagonal of a rhombus is twice the other. If the area is 128 cm2, find the shorter diagonal.
6. ABCD is a parallelogram; P and Q are points on side AB. What is the ratio area(ΔPCD) : area(ΔQCD)?
7. O is any point on diagonal PR of parallelogram PQRS. Prove area(ΔPSO) = area(ΔPQO).
8. If the midpoints of the sides of a 4-gon are joined in order, prove the area of the parallelogram formed is half the area of the 4-gon.
9. In ΔABC, D is the midpoint of BC and AD is the median; P is any point on AD. Show area(ΔABP) = area(ΔACP).
10. Square ABCD has an interior point P. What is the ratio of the red region (ΔPAB + ΔPCD) to the green region (ΔPBC + ΔPDA)?
11. In ΔABC, D is the midpoint of AB, P is any point on BC, and Q on AB with CQ ∥ PD. Prove area(ΔBPQ) = ½ area(ΔABC).
Exercise Set 6.3 (π = 22/7 unless stated)
1. Find the area of a sector of a circle of radius 7 cm if the sector angle is 60°.
2. Find the area of a quadrant of a circle whose circumference is 44 cm.
3. The minute hand of a clock is 7 cm long. Find the area swept in 10 minutes.
4. A chord of a circle of radius 10 cm subtends 90° at the centre. Find the area of the (i) minor sector and (ii) major sector. (Use π ≈ 3.14.)
5. A chord of a circle of radius 15 cm subtends 60° at the centre. Find the areas of the minor and major segments. (Use π ≈ 3.14 and √3 ≈ 1.73.)
6. A car has two non-overlapping wipers, each blade 28 cm, sweeping 120°. Find the total area cleaned in one sweep.
*7. A chord subtends 60° at the centre of a circle of radius r. Show that the minor segment area = r2(π/6 − √3/4).
*8. An equilateral triangle is inscribed in a circle of radius r. Show that area(triangle) : area(circle) = 3√3/(4π) ≈ 0.413.
*9. A square is inscribed in a circle of radius r. Show that area(square) : area(circle) = 2/π ≈ 0.637.
*10. A regular hexagon is inscribed in a circle of radius r. Show that area(hexagon) : area(circle) = 3√3/(2π) ≈ 0.827. Why is it exactly twice the answer to Q8?
Class 9 Maths Ganita Manjari Chapter 6 Solutions — End-of-Chapter Exercises
1. Draw area figures for the identities (a + b)(a − b) = a2 − b2 and (a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca.
2. An isosceles triangle has perimeter 40 cm with equal sides 15 cm each. Find its area.
3. An isosceles triangle has base 10 cm and area 60 cm2. Find the equal sides.
4. The area of a right triangle is 54 cm2; one leg is 12 cm. Find its perimeter.
5. The sides of a triangle are in the ratio 2 : 3 : 4 and the perimeter is 45 cm. Find its area.
6. The sides of a triangle are 7 cm, 24 cm, 25 cm. Find its area in two ways.
7. A bicycle wheel has diameter 60 cm. How far does the cyclist travel after the wheel rotates 100 times?
8. Find the area of a quadrant of a circle whose circumference is 66 cm.
9. A car wheel has outer radius 28 cm. How far does the car travel in one turn, and how many turns in 1 km?
*10. Two rectangles have the same area and the same perimeter. Are they congruent?
11. Using area of parallelogram = base × height and Fig. 6.42, show area of a trapezium = ½(a + b)h.
12. By dividing a trapezium into two triangles, show its area = ½(a + b)h.
13. Show how two copies of a trapezium make a parallelogram, and how this gives the trapezium area formula.
14. Show that the area of a kite is half the product of its diagonals, (i) using algebra and (ii) using geometry.
15. (i) Rectangle 2a×2b vs a×b; (ii) triangle with sides 2a,2b,2c vs a,b,c; (iii) triangle with sides 3a,3b,3c vs a,b,c — show the area ratios and check how many copies fit.
*16. What fraction of the triangle / the square is shaded (Fig. 6.43, 6.44)?
17. What fraction of each rectangle is covered by the circles (Fig. 6.45, 6.46)?
18. Make and prove a conjecture about the area occupied by circles fitted into a rectangle (test for 10, 20, 50 circles).
*19. Nine identical rectangles are fitted to make a large rectangle of area 72 cm2. Find the perimeter of each small rectangle.
*20. Show that the blue and red triangles (lines from a vertex to the trisection points of the opposite side, Fig. 6.48) have equal areas.
*21. A quarter circle (centre at a vertex) and two semicircles on adjacent sides create regions A and B (Fig. 6.49). Show A and B have equal area.
*22. Four semicircles (centres at the midpoints of the sides) inside a square of side 2 form a 4-petal flower (Fig. 6.50). Find its perimeter and area.
*23. Two concentric circles; chord BC of the larger touches the smaller, BC = l. Show the ring area between them is (1/4)πl2.
*24. Semicircles are drawn on the three sides of a right triangle (Fig. 6.52). Show Area(A) + Area(B) = Area(C).
*25. Two circles of radius r pass through each other’s centres (Fig. 6.53). Find the area of the region common to both, in terms of r.
*26. Three triangles inside a rectangle have areas A, B, C (Fig. 6.54). Show the rectangle’s area = 2(A + C)(B + C)/C.
*27. Two shaded regions are formed by a quarter circle, a semicircle and a triangle (Fig. 6.55). Show the two shaded regions are equal in area.
Common Mistakes to Avoid
Watch out for these
- Mixing up circumference (2πr) with area (πr2).
- For arcs/sectors, forgetting the (θ/360) fraction.
- In Heron’s formula, using the perimeter instead of the semi-perimeter s.
- For a segment, forgetting to subtract the triangle from the sector.
- For trapezium/rhombus/kite, forgetting the ½.
- Using the slant side as the height — the height is the perpendicular distance.
- Scaling error: doubling the sides multiplies area by 4 (not 2).
Practice MCQs & Assertion–Reason
1. The circumference of a circle of radius r is:
(a) πr2 (b) 2πr (c) πr (d) πd2
2. The area of a circle of radius r is:
(a) 2πr (b) πd (c) πr2 (d) πr
3. The area of a triangle of base b and height h is:
(a) bh (b) ½bh (c) 2bh (d) ⅓bh
4. Heron’s semi-perimeter for sides a, b, c is:
(a) a + b + c (b) (a + b + c)/2 (c) (a + b + c)/3 (d) abc
5. The area of a trapezium with parallel sides a, b and height h is:
(a) (a + b)h (b) ½(a + b)h (c) abh (d) ½ab
6. The area of a rhombus with diagonals d1, d2 is:
(a) d1d2 (b) ½d1d2 (c) 2d1d2 (d) ¼d1d2
7. If the circumference of a circle is 44 cm (π = 22/7), its radius is:
(a) 7 cm (b) 14 cm (c) 11 cm (d) 22 cm
8. The area of a sector of angle θ in a circle of radius r is:
(a) (θ/180)πr2 (b) (θ/360)πr2 (c) (θ/360)2πr (d) πr2
9. The area of an equilateral triangle of side a is:
(a) ½a2 (b) (√3/4)a2 (c) a2 (d) (√3/2)a2
10. A segment of a circle equals:
(a) sector + triangle (b) sector − triangle (c) ½ sector (d) triangle − sector
For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.
A-R 1. Assertion: The area of a circle of radius r is πr2.
Reason: Area is proportional to the square of the radius.
A-R 2. Assertion: Heron’s formula can find a triangle’s area from its three sides.
Reason: It uses the semi-perimeter s = (a + b + c)/2.
A-R 3. Assertion: A triangle with sides 7, 24, 25 has area 84 sq cm.
Reason: The triangle is right-angled, so area = ½ × 7 × 24.
A-R 4. Assertion: Doubling the radius of a circle doubles its area.
Reason: The area of a circle is πr2.
A-R 5. Assertion: A segment of a circle is the region between a chord and its arc.
Reason: A segment equals the area of the sector minus the triangle.
Quick Revision Summary
- Circle: circumference 2πr, area πr2; arc = (θ/360)2πr, sector area = (θ/360)πr2.
- Rectangle l×b; parallelogram base×height; triangle ½×base×height.
- Heron: area = √(s(s − a)(s − b)(s − c)); equilateral (√3/4)a2.
- Trapezium ½(a + b)h; rhombus/kite ½d1d2.
- Segment = sector − triangle.
- Scaling all lengths by k multiplies area by k2.
How to score full marks in this chapter
Write the correct formula first and keep units throughout. Use the π value the question specifies (22/7 or 3.14). For Heron’s problems, find the third side and s before substituting. For segments, compute the sector and the triangle separately, then subtract. Show each arithmetic step neatly.
Frequently Asked Questions
What is Class 9 Maths Ganita Manjari Chapter 6 about?
Perimeter and area of plane figures — circumference, arc length, sector perimeter, areas of rectangles, parallelograms, triangles (Heron’s formula), trapeziums, rhombuses and kites, and areas of circles, sectors and segments.
What is Heron’s formula?
For sides a, b, c with s = (a + b + c)/2, area = √(s(s − a)(s − b)(s − c)).
What is the area of a sector?
Sector area = (θ/360) × πr2, where θ is the central angle.
Are these Class 9 Maths Ganita Manjari Chapter 6 solutions free?
Yes. All solutions are free and follow the official NCERT Ganita Manjari textbook for 2026–27.
