These NCERT Solutions for Class 6 Maths Chapter 5 Understanding Elementary Shapes Ex 5.1 Questions and Answers are prepared by our highly skilled subject experts.

## NCERT Solutions for Class 6 Maths Chapter 5 Understanding Elementary Shapes Exercise 5.1

Question 1.

What is the disadvantage in comparing line segments by mere observation?

Answer:

Comparing the line segments simply by ‘observation’ may not be accurate. For example, the line segments AB and CD (in the following figure) seem to be equal, but actually they are not.

Question 2.

Why is it better to use a divider than a ruler, while measuring the length of a line segment?

Answer:

It is better to use a divider than a ruler, because the thickness of the ruler may cause difficulties in reading off the length. However, divider gives up accurate measurement.

Question 3.

Draw any line segment, say \(\begin{equation}

\overline{\mathbf{A B}}

\end{equation}\). Take any point C lying in between A and B. Measure the lengths of AB, BC and AC. Is AB = AC + CB?

[Note: If A, B, C are any three points on a line, such that AC + CB = AB, then we can be sure that C lies between A and B.]

Answer:

Yes.

\(\begin{equation}

\overline{\mathbf{A C}}

\end{equation}\) = 6.3 cm

\(\begin{equation}

\overline{\mathbf{B C}}

\end{equation}\) = 2.7 cm

\(\begin{equation}

\overline{\mathbf{A B}}

\end{equation}\) – 9.0 cm

∵ AC + BC = 6.3 cm + 2.7 cm = 9.0 cm and AB = 9.0 cm

∴ AC + BC = AB Hence verified.

Question 4.

If A, B, C are three points on a line such that AB = 5 cm, BC = 3 cm and AC = 8 cm, which one of them lies between the other two?

Answer:

∵ AB = 5 cm

∵ BC = 3 cm

∴ AB + BC = 5 cm + 3 cm = 8 cm

But AC = 8 cm

The point B lies between A and C.

Question 5.

Verify whether D is the mid-point of \(\begin{equation}

\overline{\mathbf{A G}}

\end{equation}\).

Answer:

AD = 3 units, DG = 3 units

AD = DG.

Thus, D is the mid-point.

Question 6.

If B is the mid-point of \(\begin{equation} \overline{\mathbf{A C}}\end{equation}\) and C is the mid-point of \(\begin{equation}\overline{\mathbf{B D}}\end{equation}\) where A, B, C, D lie on a straight line, say why AB = CD?

Ans.

B is the mid-point of \(\begin{equation} \overline{\mathbf{A C}}\end{equation}\).

∴ AB = BC … (i)

And C is the mid-point of \(\begin{equation} \overline{\mathbf{BD}}\end{equation}\).

∴ BC = CD … (ii)

From equation (i) and (ii), we get AB = CD

Question 7.

Draw five triangles and measure their sides. Check in each case, of the sum of the lengths of any two sides is always less than the third side.

Answer:

Yes, sum of two sides of a triangle is always greater than the third side.