Why was it easy to answer these questions without a calculator?

Question

1)They involve dividing or multiplying with multiples of 5.

2)They involve dividing or multiplying with multiples of 10.

3)They involve dividing or multiplying with multiples of 2.

Answer 1

4) They involve simple addition or subtraction.

5) They involve numbers with repeating patterns or sequences.

6) The numbers involved are easily recognizable or memorized.

7) The questions are simple and straightforward, without complex calculations required.