## Selina Concise Mathematics Class 7 ICSE Solutions Chapter 18 Recognition of Solids (Representing 3-D in 2-D)

**Selina Publishers Concise Mathematics Class 7 ICSE Solutions Chapter 18 Recognition of Solids (Representing 3-D in 2-D)**

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### Recognition of solids Exercise 18 – Selina Concise Mathematics Class 7 ICSE Solutions

**Question 1.**

**Identify the nets which can be used to form cubes**

**Solution:**

Nets for a cube are (ii) , (iii) and (v).

**Question 2.**

**Draw at least three different nets for making cube.**

**Solution:**

**Question 3.**

**The figure, given below, shows shadows of some 3D objects, when seen under the lamp of an overhead projector :**

**In each case, name the object.**

**Solution:**

**Question 4.**

**Using Euler’s formula, find the values of a, b, c and d. **

**Solution:**

**(i)**a + 6 – 12 = 2 ⇒ a = 2 – 6 + 12 = 14 – 6 = 8

**(ii)**b + 5- 9 = 2 ⇒6 = 2 + 9- 5 = 6

**(iii)**20+ 12 — c = 2 ⇒32 – c = 2 ⇒ c = 32-2 ⇒ c = 30

**(iv)**6 + d-12=2 ⇒ d – 6 = 2 ⇒ d = 2 + 6 = 8

**Question 5.**

**Dice are cubes with dot or dots on each face. Opposite faces of a die always have a total of seven on them.**

** Below are given two nets to make dice (cube), the numbers inserted in each square indicate the number of dots in it.**

Insert suitable numbers in each blank so that numbers in opposite faces of the die have a total of seven dots.

**Solution:**

**Question 6.**

**The following figures represent nets of some solids. Name the solids**

**Solution:**

The given nets are of the solid as given below :

**(i)** Cube

**(ii)** Cuboid

**Question 7.**

**Draw a map of your class room using proper scale and symbols for different objects.**

**Solution:**

**Question 8.**

**Draw a map of your school compound using proper scale and symbols for various features like play ground, main building, garden, etc.**

**Solution:**

**Question 9.**

**In the map of India, the distance between two cities is 13.8 cm.**

** Taking scale : 1 cm = 12 km, find the actual distance between these two cities.**

**Solution:**

The scale for a map is given to be 1 cm = 12 km

The distance between these two cities = 13.8 cm on the map

∴ Actual distance between these two cities

= 12 x 13.8 km = 165.6 km