BdMO National 2013: Primary 2, Junior 1

[BdMO]

Nazia’s mobile phone has a strange problem. Each time she sends an SMS, it is also sent to all the existing numbers of her call list. The actual recipient of the SMS is then added to her call list.. At some point, Nazia deleted her call list. The next SMS she sent was the $16^{th}$ SMS sent from her mobile phone. How many numbers were there in her call list before she deleted her call list?

[atiab jobayer]

I think it will be 15 day.because when she send the last message it was the 16th message after clearing message.

[*Mahi*]

Please do not use red color in general posts in forum, as it is generally associated and can be confused with warnings or notices.

[atiab jobayer]

Please do not use red color in general posts in forum, as it is generally associated and can be confused with warnings or notices.

But Mahi, I've used blue colour. Not RED.

[*Mahi*]

That was because I edited the post. Forgot to clarify that part, sorry.

[tanmoy]

The answer is:$1+2+3+4+.......+15=120$

[Raiyan Jamil]

I think there were 5 numbers. Because, after sending the first message, there will be 1 number in the call list . And in the next message, there will be 2 numbers in the call list and 3 messages in the message box(as 1+2=3). Then, going like this we will see that there are 5 numbers in the call list and 15 messages in the message box(as 1+2+3+4+5=15). And deleting all the numbers and sending a new message, then it will be the 16th message.
So, that is why I think there were 5 numbers. Someone please clarify if my answer is right or wrong.

[samiul_samin]

the correct answer is 5.

[M. M. Fahad Joy]

the correct answer is 5.

Mr. Intelligent brother,
Why have you mixed the call list with message list?

[samiul_samin]

the correct answer is 5.

Mr. Intelligent brother,
Why have you mixed the call list with message list?

They are connected.See the previous posts again.