they say that no. ending with 1 4 5 6 and 9 is perfect square no. then why is 1989 is non perfect though it has 9 at unit place.plz ans
Answers
Step 1:
What is the last number of 1,989? It is this number: 1989. The answer is 9. Is 9 in the list of numbers that are never perfect squares (2, 3, 7 or 8)?
Answer: NO, 9 is not in the list of numbers that are never perfect squares. Let's continue to the next step.
Step 2:
We now need to obtain the digital root of the number. Here's how you do it:
Split the number up and add each digit together:
1 + 9 + 8 + 9 = 27
If the answer is more than one digit, you would add each digit of the answer together again:
2 + 7 = 9
What is the digital root of number 1,989?
Answer: 9
Step 3:
So now we know the digital root of 1,989 is 9. Is 9 in the list of digital roots that are always a square root (1, 4, 7 or 9)?
Answer: YES, 9 is in the list of digital roots that are always perfect squares. We can conclude that 1,989 could be a perfect square!
Factoring:
OK, so now we know that 1,989 could be a perfect square. We have to find the factors of the number to be sure.