EN हिं

NCERT Solutions for Class 5th Maths Chapter 11 Your classroom floor, five grid shapes, everyday objects, and three word problems — Let Us Do

Book page 151–153 Updated on2026-09-19

Q1.
Find the area of your classroom floor in square meters. Take the help of your teacher to measure the length and breadth of the floor. What is the perimeter of the classroom floor?
Answer

Measure the two sides with a measuring tape, then multiply for the area and add all four sides for the perimeter. A common Indian classroom is about 8 m by 6 m, which gives an area of 48 square m and a perimeter of 28 m.

  1. Measure the length. Lay the measuring tape along the longer wall, at floor level. Suppose it reads 8 m.
  2. Measure the breadth. Now measure the shorter wall. Suppose it reads 6 m.
  3. Find the area. Area = Length × Breadth = 8 × 6 = 48 square m.
  4. Find the perimeter. Perimeter = 8 + 6 + 8 + 6 = 28 m, or 2 × (8 + 6) = 2 × 14 = 28 m.
Length of floor = 8 m
Breadth of floor = 6 m
Area = 8 m × 6 m = 48 square m
Perimeter = 2 × (8 + 6) = 2 × 14 = 28 m
Why the unit is square metres and not square centimetres: A classroom floor would take thousands of 1 cm squares — far too many to think about. So we use a bigger tile: a square 1 m by 1 m. Counting in square metres keeps the number small and sensible.
Sample answer: “Our classroom floor is 8 m long and 6 m broad. Its area is 48 square m and its perimeter is 28 m.” Measure your own room and write your own numbers.
Q2.
Find the area and perimeter of the following shapes. (a)
(a)____ cm____ cm
Shape (a) on a 1 cm square grid. Measure its two sides.
Answer

Shape (a) is a square of side 6 cm. Area = 36 square cm. Perimeter = 24 cm.

Shape (a): 6 cm by 6 cm
Six rows of six squares. All four sides are equal, so it is a square.
  1. Count along the bottom. 6 squares, so the length is 6 cm.
  2. Count up the side. 6 squares, so the breadth is also 6 cm.
  3. Area. 6 × 6 = 36 square cm.
  4. Perimeter. All four sides are 6 cm, so 4 × 6 = 24 cm.
Area = 6 cm × 6 cm = 36 square cm
Perimeter = 4 × 6 cm = 24 cm
Q3.
Find the area and perimeter of the following shapes. (b)
(b)____ cm____ cm
Shape (b) on a 1 cm square grid. Measure its two sides.
Answer

Shape (b) is a rectangle 4 cm long and 7 cm broad. Area = 28 square cm. Perimeter = 22 cm.

Shape (b): 4 cm across, 7 cm down
Seven rows of four squares.
  1. Count across. 4 squares → 4 cm.
  2. Count down. 7 squares → 7 cm.
  3. Area. 4 × 7 = 28 square cm.
  4. Perimeter. 2 × (4 + 7) = 2 × 11 = 22 cm.
Area = 4 cm × 7 cm = 28 square cm
Perimeter = 2 × (4 + 7) = 22 cm
Check it yourself: Walk round the outline: 4 + 7 + 4 + 7 = 22. The short cut gives the same answer.
Q4.
Find the area and perimeter of the following shapes. (c)
(c)____ cm____ cm
Shape (c) on a 1 cm square grid. Measure its two sides.
Answer

Shape (c) is a rectangle 12 cm long and 4 cm broad. Area = 48 square cm. Perimeter = 32 cm.

Shape (c): 12 cm across, 4 cm down
Four rows of twelve squares.
  1. Count across. 12 squares → 12 cm.
  2. Count down. 4 squares → 4 cm.
  3. Area. 12 × 4 = 48 square cm.
  4. Perimeter. 2 × (12 + 4) = 2 × 16 = 32 cm.
Area = 12 cm × 4 cm = 48 square cm
Perimeter = 2 × (12 + 4) = 32 cm
Compare with shape (a): Shape (a) has a perimeter of 24 cm and an area of 36 square cm. Shape (c) has a longer perimeter, 32 cm, and a bigger area too. But remember from page 148 that this does not always happen.
Q5.
Find the area and perimeter of the following shapes. (d)
(d)____ cm____ cm
Shape (d) on a 1 cm square grid. Measure its two sides.
Answer

Shape (d) is a square of side 3 cm. Area = 9 square cm. Perimeter = 12 cm.

Shape (d): 3 cm by 3 cm
Three rows of three squares.
  1. Count across. 3 squares → 3 cm.
  2. Count down. 3 squares → 3 cm. All four sides are equal, so it is a square.
  3. Area. 3 × 3 = 9 square cm.
  4. Perimeter. 4 × 3 = 12 cm.
Area = 3 cm × 3 cm = 9 square cm
Perimeter = 4 × 3 cm = 12 cm
Q6.
Find the area and perimeter of the following shapes. (e)
(e)____ cm____ cm
Shape (e) on a 1 cm square grid. Measure its two sides.
Answer

Shape (e) is a rectangle 6 cm long and 5 cm broad. Area = 30 square cm. Perimeter = 22 cm.

Shape (e): 6 cm across, 5 cm down
Five rows of six squares.
  1. Count across. 6 squares → 6 cm.
  2. Count down. 5 squares → 5 cm.
  3. Area. 6 × 5 = 30 square cm.
  4. Perimeter. 2 × (6 + 5) = 2 × 11 = 22 cm.
Area = 6 cm × 5 cm = 30 square cm
Perimeter = 2 × (6 + 5) = 22 cm

All five answers together:

ShapeLengthBreadthAreaPerimeter
(a)6 cm6 cm36 square cm24 cm
(b)4 cm7 cm28 square cm22 cm
(c)12 cm4 cm48 square cm32 cm
(d)3 cm3 cm9 square cm12 cm
(e)6 cm5 cm30 square cm22 cm
Notice: Shapes (b) and (e) both have a perimeter of 22 cm, but their areas are 28 and 30 square cm. Same lace, different cloth — exactly what we explored on page 148.
Q7.
Find the area and perimeter of the following objects. Use a scale or measuring tape to find the length and the breadth of each of the objects. (Notebook cover, newspaper, blackboard, ludo board, and two objects of your own.)
Answer

Measure each object, then use Area = Length × Breadth and Perimeter = 2 × (Length + Breadth). Here is a completed table with sizes that are typical — measure your own things and write your own numbers.

S. No.Name of the objectLengthBreadthAreaPerimeter
1.Cover of the notebook28 cm21 cm588 square cm98 cm
2.Newspaper (one open sheet)55 cm37 cm2035 square cm184 cm
3.Blackboard300 cm120 cm36000 square cm840 cm
4.Ludo board30 cm30 cm900 square cm120 cm
5.Your maths textbook25 cm19 cm475 square cm88 cm
6.Your desk top60 cm40 cm2400 square cm200 cm

How one row was worked out — the notebook cover:

  1. Measure the long side with a scale: 28 cm.
  2. Measure the short side: 21 cm.
  3. Area = 28 × 21. Do it in two easy pieces: 28 × 20 = 560 and 28 × 1 = 28. Add: 560 + 28 = 588 square cm.
  4. Perimeter = 2 × (28 + 21) = 2 × 49 = 98 cm.
Area of notebook cover = 28 cm × 21 cm = 588 square cm
Perimeter of notebook cover = 2 × 49 = 98 cm
Tip for measuring: Always start at the 0 mark of the scale, not at the very end of the plastic. Keep the scale straight along the edge, and read the number where the object stops.
Q8.
Find the area of a rectangular field whose length is 42 m and breadth is 34 m.
Answer

Area = 1428 square m.

  1. Name what we must find. The area of a rectangular field.
  2. Write what is given. Length = 42 m, Breadth = 34 m.
  3. Use the rule. Area of a rectangle = Length × Breadth = 42 × 34.
  4. Multiply in two easy steps. 42 × 30 = 1260 and 42 × 4 = 168.
  5. Add the two parts. 1260 + 168 = 1428.
Area = Length × Breadth
Area = 42 m × 34 m
42 × 30 = 1260
42 × 4 = 168
1260 + 168 = 1428
Area = 1428 square m
Why the unit is square m: Both sides were measured in metres, so the tiles that fill the field are squares 1 m by 1 m. There are 1428 of them.
Check it yourself: The answer should be a bit less than 42 × 35 = 1470 and a bit more than 40 × 34 = 1360. Our 1428 sits neatly between them, so it is sensible.
Q9.
The area of a rectangular garden is 64 square m and its length is 16 m. What is its breadth?
Answer

Breadth = 4 m.

  1. Name what we must find. The breadth of the garden.
  2. Write what is given. Area = 64 square m, Length = 16 m.
  3. Turn the area rule around. Length × Breadth = Area, so Breadth = Area ÷ Length.
  4. Divide. 64 ÷ 16 = 4.
Area = Length × Breadth
64 = 16 × Breadth
Breadth = 64 ÷ 16
Breadth = 4 m
Why we divide here: The garden is made of 16 unit squares in every row. Sharing all 64 unit squares into rows of 16 tells us how many rows there are — that is, how many metres the breadth measures. 64 shared into groups of 16 gives 4 groups.
Check it yourself: 16 m × 4 m = 64 square m, which is exactly the area we were given. ✓ The perimeter of this garden, if you want it, is 2 × (16 + 4) = 40 m.
Q10.
Find the area of the following figure with the dimensions as marked in the figure.
32 cm6 cm12 cm
The figure with the lengths marked on it. The dotted lines are only guide lines.
Answer

Area = 576 square cm.

32 cm6 cm12 cmtop part: 32 × 6bottom part: 32 × 12
The dotted lines split the figure. Its full height is 6 + 12 = 18 cm.
  1. Read the width. The arrow across the top says the figure is 32 cm wide.
  2. Find the full height. The side is marked in two pieces, 6 cm at the top and 12 cm below. Add them: 6 + 12 = 18 cm.
  3. Use the rectangle rule. Area = Length × Breadth = 32 × 18.
  4. Multiply in two easy steps. 32 × 10 = 320 and 32 × 8 = 256.
  5. Add. 320 + 256 = 576.
Width = 32 cm
Height = 6 cm + 12 cm = 18 cm
Area = 32 cm × 18 cm
32 × 10 = 320
32 × 8 = 256
320 + 256 = 576
Area = 576 square cm
A second way, using the dotted lines: Cut the figure along the dotted line into a top strip and a bottom strip. Top strip = 32 × 6 = 192 square cm. Bottom strip = 32 × 12 = 384 square cm. Add them: 192 + 384 = 576 square cm. The same answer, which tells us both methods are right.
Careful: Do not use 6 cm or 12 cm on its own as the height. Neither one reaches all the way down the side. Only 6 + 12 = 18 cm does.
Was this helpful?