Batman challenged Superman to find the number of permutations of the word 'BATMAN' and Superman challenged Batman to find the position of 'SUPERMAN' in the dictionary made by rearranging its letters. If Batman's answer was x and Superman's was y , find the value of x + y , assuming both are good in maths!
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The number of ways we can permute the letters of the
B
A
T
M
A
N
is
6
!
/
2
!
=
3
6
0
.
The position of
S
U
P
E
R
M
A
N
in the dictionary is
7
!
×
6
+
6
!
×
6
+
5
!
×
4
+
4
!
+
3
!
×
3
+
2
!
+
1
=
3
5
0
8
5
.
Therefore
x
+
y
=
3
5
0
8
5
+
3
6
0
=
3
5
4
4
5
.
Correct. Exact solution. +1
@Ayush Rai Is there any shortcut for calculating position in dictionary?
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This is the only method I know. Its not too long.
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For superman:
A _ _ _ _ _ _ _ 7!
E _ _ _ _ _ _ _ 7!
M _ _ _ _ _ _ _ 7!
N _ _ _ _ _ _ _ 7!
P _ _ _ _ _ _ _ 7!
R _ _ _ _ _ _ _ 7!
SA_ _ _ _ _ _ 6!
SE_ _ _ _ _ _ 6!
SM_ _ _ _ _ _ 6!
SN_ _ _ _ _ _ 6!
SP_ _ _ _ _ _ 6!
SR_ _ _ _ _ _ 6!
SUA_ _ _ _ _ 5!
SUE_ _ _ _ _ 5!
SUM_ _ _ _ _ 5!
SUN_ _ _ _ _ 5!
SUPA_ _ _ _ 4!
SUPEA_ _ _ 3!
SUPEM_ _ _ 3!
SUPEN_ _ _ 3!
SUPERA_ _ 2!
SUPERMAN 1
So x = 7 ! × 6 + 6 ! × 6 + 5 ! × 4 + 4 ! + 3 ! × 3 + 2 ! + 1 = 3 5 0 8 5
For Batman:
Number of letters=6, same pair=1. So number of permutations=
y = 2 6 ! = 3 6 0
Required answer= x + y = 3 5 0 8 5 + 3 6 0 = 3 5 4 4 5