Me, DD1, DD2 travelling in auto.
DD1: how many more minutes to reach destination?
Me: 20 minutes
DD1: if you add 20 chocolates to 20 chocolates, how many do you have in total?
Me: 20 plus 20 will be 40
DD1: If you add 20, 20, 10, how much will it be?
Me: 20 plus 20 is 40, plus 10 is 50
DD2: no, if you add 20, 20, 10, how much?
Me: yes, 20 plus 20 is 40, plus 10 is 50
DD2: if you add 20 and 30?
Me: 20 plus 30 will be 50 or same as, 20 plus 20 plus 10
DD2: If you add another 10, it becomes 60
If you add another ten, it becomes 70, that way we keep adding 10, we reach 100, is it?
And I've kept wondering how one should introduce the fact that 10,20,30,40 and so on are all separated by 10, that when you keep adding 10 to 10 and it's sum consecutively, you get multiples for 10, that when you write numbers in 10 by 10 matrix, every two numbers in adjacent rows of the same column are separated by 10. Kids are at their best, learn the best, when on their own. Indeed true!
It's all a journey of learning that starts with a curious child, not a rigid system.