Question by  Juilebasham (5)

Where can I get help with number stairs?

My teacher explained them but I don't get it.


Answer by  Clement (1453)

The number stairs are characterized by the basic number (x) and the height (h). So the sum will be x+(x+1)+...+(x+h-1) + (x+10)+(x+11)+...+(x+10+h-2) + ... + x+(h-1)*10. For multiplication you get x+(x+1)+...+(x+h-1) * (x+10)+(x+11)+...+(x+10+h-2) * ... * x+(h-1)*10. Keep in mind that x+(x+1)+...+(x+h-1) equals (x+x+h-1)/2*h. Hence the some becomes (2x+h-1)/2*h + (2x+20+h-2)/2*(h-1) + x+(h-1)*10, which can further be simplified.


Answer by  marlee (40)

I'm sure your teacher wouldn't mind staying after class or before class to help you. They get paid to help students succeed. Teachers don't like to see their students fail, because then that is just proof they aren't doing their job to the fullest, teaching you important information.

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