One day, Mr Tan tested his five children, "Suppose I count from 1 to 2015 on my left hand's fingers. I begin on my thumb and work my way to my little finger and back to my thumb again (without skipping a finger) and just keep repeating this. On which finger will I count 2015?"

The answers given by his children were:

James Charles: "Thumb."

Santa Claus: "Index finger."

Ronaldo: "Middle finger."

Alfred: "Ring finger."

John Cena: "Little finger."

Details and assumptions:

Mr Tan has five fingers on a hand like anyone else haha.

Mr Tan counts exactly one number for each finger.

Whenever Mr Tan reaches his thumb or little finger, he counts only one number there, after which he reverses direction.

Yes, one of the five siblings MUST be correct. But which one???

Guest Nov 17, 2019

#1**+1 **

There are 2015 counts.

Using your fingers, you can count STARTING with your thumb, and counting to your little finger, then ending back on your index finger. You just counted 8 times.

The next count will start a new sequence on your thumb beginning with 9.

So each time we start a new sequence, the counts increase by 8, with the next count being the thumb.

So we can divide 2015 by 8 and find the remainder through long division.

We find that the remainder is 7.

So all we need to do is count from 1 - 7 starting with your thumb, and work your way to your little finger and back to your thumb again.

I can leave that up to you. (It should be easy to count your fingers)

If you want to check, Ronaldo should be the answer.

CalculatorUser Nov 17, 2019

#6**0 **

When I hold down my mouse button and swipe across the blacked out section, I see that underneath it says Ronaldo. That isn't the answer every one else is finding.

_{.}

Guest Nov 17, 2019

#7**0 **

Everyone is finding the middle finger.

And that is Ronaldo.

The question is asking which sibling, not which finger

You are convincing me to give a middle finger to you, Guest. grrr.....

CalculatorUser
Nov 17, 2019

#2**0 **

CU: Did you read this part of the question:

Mr Tan counts **exactly one number for each finger.**

**Whenever Mr Tan reaches his thumb or little finger, he counts only one number there, after which he reverses direction.**

Guest Nov 17, 2019

#3**0 **

Yes I did

^{Using your fingers, you can count STARTING with your thumb, and counting to your little finger, then ending back on your index finger. You just counted 8 times.}

Based on your statement, the quote above is correct.

CalculatorUser
Nov 17, 2019

#4**+1 **

THX, CU !!!

Here's my idea :

After every 72 numbers, the next number lands back on the thumb

So

2105 = 27 (72) + 71

And

71 / 9 = 7* 9 + 8

So

7 fingers of a cycle of 9 each starting with the thumb puts us at the middle finger...and 8 more fingers after this lands us back on the middle finger

CPhill Nov 17, 2019

#5**+1 **

OK. I went another route! Started with 1 at the Thumb and ended in 5 at "Little Finger". Thereafter, you end on the "Little Finger" every 8 counts, so that you have an AP:

5, 13, 21, 29...........2013 being the last term on the Little finger. Then reverse count 2014 on the "Ring Finger" and 2015 on the "Middle Finger"!!.

Guest Nov 17, 2019