Question

find the missing digit x to make perfect square of 2220x

Answer 1

To find the missing digit given number 2220*.

Some points to be noted down:

Square numbers only end in 1, 4, 5, 6, 9, 0. And also they have digit sums of 1, 4, 7, 9

We have following choices:

a) 22201

b) 22204

c) 22205

d) 22206

e) 22209

f) 22200

Now, we will check the digital sum of each of the above numbers and note them down.

a) 2+2+2+0+1 = 7

b) 2+2+2+0+4 =1

c) 2+2+2+0+5 = 2 ( This cannot be the answer)

d) 2+2+2+0+6= 12= 1+2 =3 ( This cannot be the answer)

e) 2+2+2+0+9= 15 = 1+5=6 ( This cannot be the answer)

f) 2+2+2+0+0 = 6 ( This also cannot be the answer).

Hence our answers might be either 22201 or 22204

We will have 22201 as the perfect square. Please correct me if i’m wrong

Contradiction:

If a number has a valid digit sum and a valid last figure that does not mean that it is a square number.