Page 85 - Concepts of Reasoning-8

Example 2. Find the minimum number of straight lines in the given figure.

(a) 14 (b) 16 (c) 12 (d) 15

Solution (a). Given figure is
A
Lines are :
I H
Horizontal lines: BE, FG, CD ® 3 K
B E
Vertical lines: AL ® 1
J K
Slanting lines: AB, BC, AE, ED, AC, AD, BD, CE, IJ, HK ® 10
So, there are 3 + 1 + 10 = 14 lines. F G
Thus , option (a) is correct. C L D

Type 2. Problems based on sitting arrangement:
Example 3. Eight friends A, B, C, D, E, F, G and H are sitting around a circle facing the centre. E is
third to the left of G, who is on the immediate right of B, who is third to the left of A. H is
second to the right of F, who is not an immediate neighbour of E. D is not an immediate
neighbour of B. Which of the following pairs has the first person on the immediate left of

the second person? (IMO 2017)
(a) GB (b) AF (c) CE (d) HD
Solution (d). Eight friends A, B, C, D, E, F, G and H will sit around a circle B

facing the centre as shown below: G C
Here, H is to the immediate left of D.
F E
Thus, option (d) is correct.

A D
EXERCISE H
EXERCISE
1. Find the number of rectangles contained in the figure below:

(a) 8 (b) 10 (c) 12 (d) 9
2. Find the number of triangles contained in the figure below:

(a) 19 (b) 23 (c) 21 (d) 29

85 Reasoning - 8