a. Write down a secret number, which can be any whole number

Question

Multiply by 5
Add 2
Multiply by 4
Add 2
Multiply by 5
Subtract 50

Drop the two zeros at the end.

Do you recognize the result?

B. Let S stand for a secret number that you begin with in part (a). Write an expression in terms of S that shows the result of applying the steps in part (a). Apply properties of arithmetic to this expression to explain why the end result of the steps in part (a) is always predictable.

Answer 1

{[(5s+2)4]+2}5 - 50

{20s+8+2}5 - 50

100 s + 50 - 50

100 s

drop two zeros and get s

Answer 2

17
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