Expert: Chen Min - 1/6/2011

Question
"write the rule for each given function table below"

Input  2 4  7  8 10
Output 3 7 13 15 19
Rule: ___________________

Can you help?

Answer
It's not actually advanced math Qn....but the hell with it.
Since this looks like a homework question, I'll give you a hint only
You see, the rule should apply to all inputs, so if you guess one that works on the first input-output combination, it must be further confirmed by the rest.

What's the quickest guess? 3=2+1, right? fair enough. But for the second pair, 4+1 does not equal 7, but 5. For the rest, you'll see the gap between input+1 and the output gets wider and wider. So the rule certainly cannot be as simple as an addition, right?

But what comes to your mind when the input gets larger (from 2 to 10), it's gap to the output gets larger also (from 3-2=1 to 19-10=9)? Don't you see the output is some kind of multiple to the input? (Not exactly, of course, but approximately, right?)

And after you work out the correct multiplier on input, do you now see the result is very orderly with respect to the output? ^^ Work it out, you're capable of this.