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Mathematics
A seven-digit number made up of all distinct digits 8, 7, 6, 4, 2, x and y is divisible by 3 then possible number of order pair (x, y) is
Q. A seven-digit number made up of all distinct digits
8
,
7
,
6
,
4
,
2
,
x
and
y
is divisible by 3 then possible number of order pair
(
x
,
y
)
is
713
98
Permutations and Combinations
Report Error
A
4
B
8
C
10
D
12
Solution:
Sum of digits
=
8
+
7
+
6
+
4
+
2
+
x
+
y
=
27
+
x
+
y
For divisible by 3 , sum must be divisible by 3
∴
pairs of
x
and
y
is
(
0
,
3
)
,
(
0
,
9
)
,
(
3
,
0
)
,
(
9
,
0
)
,
(
1
,
5
)
,
(
3
,
9
)
,
(
5
,
1
)
,
(
9
,
3
)
out of
0
,
1
,
3
,
5
,
9
Number of order pair
(
x
,
y
)
is
8.
