Explanation
If the number of rows and number of columns are to be equal, then the total number of trees will be in the form of x2, which is nothing but a perfect square.
As 1000 is not a perfect square, you need to check for a perfect square above and nearest to 1000.
It's 1024, which is square of 32.$$\text{ So he needs to add 24 more trees to get 1024.}$$
$$25$$ is the only perfect square which falls between $$20$$ and $$30$$.
Therefore, option C is correct.
The numbers which will have $$1$$ at their unit place in their squares are the numbers ends with $$1$$ or $$9$$
Because $$1\times1$$ $$=$$ $$1$$ and $$9 \times 9 = 81$$
Here, $$225 = 3 \times 3 \times 5 \times 5 = (3 \times 5)^2 = (15)^2$$
Therefore, option C is the correct answer.
In $$(64)^2$$, the digit in unit's place is the last digit at the multiplication of
$$4 \times 4 = 1\underline{6}$$
So, $$6$$ at units place
Therefore, B is the correct answer.
Since, the last digit of number $$427$$ is $$7$$, $$7$$ being an odd number the whole square number will be odd because $$7 \times 7 = 49$$
Thus, square root of an odd number is odd
Therefore, option B is the correct answer.
We know
$$11^2 = 121$$ comes before $$140$$
$$12^2 = 144$$ lies between $$140$$ $$\&$$ $$150$$
$$13^2 = 169$$ lies after $$150$$
Only$$ 144$$ lies between $$140$$ & $$150$$
So $$144$$ is the only perfect square number between $$140$$ & $$150$$
Only $$81$$ is a perfect square number between $$ 80$$ & $$90$$.
$$9^2= 81$$,
$$10^2 = 100$$, before its $$8^2= 64$$ .
$$(64, 81, 100$$) only $$81$$ lies between $$80$$ & $$90$$.
$$\textbf{Step -1: Find prime factors of 625.}$$
$$\text{Prime factors of }625=5\times5\times5\times5.$$
$$\textbf{Step -2: Find the square root of 625.}$$
$$\sqrt{625}=\sqrt{5\times5\times5\times5}$$
$$=5\times5$$
$$=25$$
$$\textbf{Hence, B is the correct option.}$$
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