Selina Concise Class 7 Math Chapter 18 Recognition of Solids Exercise 18 Solution
EXERCISE 18
(1) (i), (ii) and (v)
(4)
Faces | a | 5 | 20 | 6 |
Vertices | 6 | b | 12 | d |
Edges | 12 | 9 | c | 12 |
(i) a + 6 – 12 = 2
⇒ a – 6 = 2
⇒ a = 2 + 6 = 8
(ii) b + 5 – 9 = 6
⇒ b – 4 = 6
⇒ b = 6 + 4 = 10
(iii) 20 + 12 – c = 2
⇒ 32 – c = 2
⇒ – c = 2 – 32
⇒ – c = – 30
⇒ c = 32
(iv) 6 + d – 12 = 2
⇒ d – 6 = 2
⇒ d = 2 + 6 = 8
(6) (i) cube
(ii) Cuboid
(9) Given, 1 cm = 12 km
The distance between two cities = 13.8 cm
∴ Actual distance between two cities = (13.8 × 12) km = 165.6 km
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