I spend the last two days learning about permutation and combination, all to solve a grade 7 ICAS maths question.
The fact that I only studied maths till grade 10 and that too in Malayalam has made it very difficult for me to remember much of what I studied. So I had to buy a grade 10 text book and go through it again.
The question that I was trying to solve was
The bank machine has four rows of buttons
1 2 3
4 5 6
7 8 9
Sam has a 4 digit bank number that uses one button from each row. For eg his bank number could be 0571.
How many different possibilities for Sam’s number are there.
Initially I thought there could be 3 choice from row 1, 3 from row 2 so on so forth.
And i got the answer 27. That made no sense. There had to be more than 27 combination of numbers, or anyone could hack the ATM pin code. (I know I don’t think like most and have a weird sense of logic)
This morning I finally figured , perhaps I need to look at the numbers 0471,0852, and 0963
That would give 24 ( 4 digit number 4 X 3 X 2 X 1) combination of each number. So 72 combinations.
Am I right?
Update: I just looked at the numbers again and I miseed so many numbers…for eg 0753, 0752, 08630841 etc etc.
So there has to be an eqation. What am I missing?
Now this brings me to my heartache for the day.
I, as an adult couldn’t solve a question like this, why would I want to make my child even attempt this question? Why would I frustrate them when they don’t get the answer?
Then again I firmly believe practice makes perfect.
I know Senna ( I am forever in love with him) wouldn’t have been 3 time champion if he hadn’t worked hard to get it ( That reminds me, it is 16 years this month)
Do I get my children to practice all these questions, so they can do the test well? What would they gain if they get High distinction? Where do i draw the line?