Question

6) If a and b are natural numbers, then which of the following must also be a natural number?

Answer 1

a - b is NOT always natural. Eg 4 - 7 = -3 therefore not in the natural number set.

ab is always natural

a/b is NOT always natural. Eg 4/7

So the answer to the question is (b) only II must be a natural number answer.

Answer 2

The correct answer is option b) II only.

If a and b are natural numbers, then the following must also be a natural number:

I. a - b

II. ab

III. a/b

Option I is not always true. For example, if a = 3 and b = 5, then a - b = -2, which is not a natural number. Therefore, option a) I only is not correct.

Option II is always true. The product of two natural numbers is always a natural number. Therefore, option b) II only is correct.

Option III is not always true. For example, if a = 5 and b = 2, then a/b = 2.5, which is not a natural number. Therefore, option c) III only is not correct.

Since options I and III are not always true, option d) I and II only and option e) II and III only are also not correct.

Therefore, the correct answer is option b) II only.