Question

Write 5 numbers which you cannot decide just by looking at their unit digit whether they are square numbers or not. Give an explanation too.

Answer 1

Answer:

Any natural number ending in 0, 1, 4, 5, 6 or 9 can be or cannot be a square-number. Five such numbers are:

56790, 3671, 2454, 76555, 69209

Property 2. If a number has 1 or 9 in the unit’s place, then its square ends in 1.

For example:

(1)2 = 1, (9)2 = 81, (11)2 = 121, (19)2 = 361, (21)2= 441.

Another answer is

Write five numbers which you cannot decide just by looking at their units digit (or units place) whether they are square numbers or not. The five numbers can be :- 521, 655, 124, 729, 1940 etc. Basically, numbers ending with 0, 1, 4, 5, 6 or 9 at units place can be square numbers