Quantitative Aptitude :: Problems on Numbers - Discussion

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Explanation:
Let the numbers are 2a +1, 2a + 3, 2a + 5, 2a + 7 and their sum = 8a + 16
Given that if this sum is divided by 10, results in a perfect square.
So, (8a+16)/10 = k^2.
=> a = (10k^2?16) /8
=> a=[ 5(k^2)/4 ]?2
As k^2 is a perfect square and has to be divided by 4, only even numbers should be considered for k.
For k = 2, we get, a = 3, but 2a + 1 is not a two digit number.
For k = 4, a = 18 for which the given condition is satisfying.
So the numbers are 37, 39, 41, 43.
For k = 6, a = 43. The number are 87, 89, 91, 93.