For example: This question
> Why is 1+0 = 1 and not 10
Attempt to find an answer will generate more questions and it is a journey down the rabbit hole. Sometimes you don't want to do that.
And upto high-school I learnt things that were based on assumptions that I kept questioning. Internet brought be some peace in my college years. Unfortunately, nowadays internet is also filled with fake/wrong/hoax/biased stuff.
First, hold one apple in each hand. Ask your child how many apples you have in one hand, them the other hand, then the total.
Then, hold two apples in one hand, with the other hand empty. Point out that you have two in one hand, and none, therefore zero, in the other. Have your child count the total number of apples, 2, and explain further how zero stands for no quantity. How when you have zero of something, you really have none.