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NCERT solution class 7 chapter 15 Visualising solid shapes 15.4 mathematics

EXERCISE 15.4


Page No 289:

Question 1:

A bulb is kept burning just right above the following solids. Name the shape of the shadows obtained in each case. Attempt to give a rough sketch of the shadow. (You may try to experiment first and then answer these questions).

Answer:

The shapes of the shadows of these figures will be as follows.

(i) A ball

The shape of the shadow of a ball will be a circle.

(ii) A cylindrical pipe

The shape of the shadow of a circular pipe will be a rectangle.

(iii) A book

The shape of the shadow of a book will be a rectangle.

Question 2:

Here are the shadows of some 3−D objects, when seen under the lamp of an overhead projector. Identify the solids (s) that match each shadow. (There may be multiple answers for these!)

Answer:

The given shadows can be obtained in case of the following objects.

  1. Compact disk
  2. A dice
  3. Triangular pyramid
  4. Note Book

Page No 290:

Question 3:

Examine if the following are true statements:

(i) The cube can cast a shadow in the shape of a rectangle.

(ii) The cube can cast a shadow in the shape of a hexagon.

Answer:

A cube can cast shadow only in the shape of a square. Therefore, any other shapes are not possible.

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