Exercises
369
19. The Hall of Horrors at an amusement park challenges you to enter at the Start door
and find your way to the Escape door. After passing through a door, the door closes
and locks. How many doors can you leave closed as you find your way from the Start
door to the Escape door? The layout of the Hall of Horrors is shown below.
Start
A
B
C
D
G :
F
E
H
I
Q
0
N
K
R -,
-4 -
P
I
M
L
L I
Escape
20. A real estate agent wants to show the three houses shown. Lay out a tour that goes
through each door.
2
3
4
5
2
3
4
6
7
8
9
1
10
11
12
13
]E
FF4
-
-EHouse with 18 doors
House with 31 doors
(a)
(b)
2
3
6
5
4
House with 19 doors
(c)