A number is said to be a 'zeroth number' if the sum of the squares of its digits ends in a zero. How many two-digit 'zeroth numbers' are there?
17
Let the number be 10x + y.
Then, 1≤x≤9, 0,≤y≤9 and x2+y2=10k.
xx2y2 must end inPossible value of y1193,72464,63911,941642,85255563642,874911,986464,698193,7
The required number = 17, hence option (d).