Consider four-digit numbers for
which the first two digits are equal and the last two digits are also equal.
How many such numbers are perfect squares?
(1)3
(2)2
(3) 4
(4)1
Any four digit number in which
first two digits are equal and last two digits are also equal will be in the
form 11 × (11a + b) i.e. it will be the multiple of 11 like 1122, 3366, 2244, .
. . .
Now, let the required number be aabb.
Since aabb
is a perfect square, the only pair of a and b that satisfy the above mentioned
condition is a = 7 and b = 4
Hence, 7744 is a perfect square