If encounter a question where I need to choose numbers, which numbers should I choose?
Are there numbers which are most suitable?
I have learnt that 0 is that good number to choose from a Kaplan video session.

In general, choose whichever numbers seem like they'll make the math easiest. Those numbers will typically be small(ish), round, and sometimes they'll be multiples of other numbers in the problem.

In even/odd problems in particular, try 0 and 1.

In positive/negative problems, try 1 and -1.

In percent problems, try 100.

In ratio problems, try the numbers in the ratios you're given. For instance, if the ratio of boys to girls is 10 to 3, start out with 10 boys and 3 girls. Or, use an easy multiple of those numbers, like 100 boys and 30 girls.

If you begin choosing numbers and the math doesn't seem to be working out correctly, you have a choice to make: do you keep working, using the not-so-good numbers? Or do you back up and pick easier numbers instead? That depends on how comfortable you are with doing pen-and-paper arithmetic. Even if the numbers start to look weird, you may be able to finish the problem anyways.
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