How old is he?

Algebra Level 1

Yesterday, I spoke with an intelligent boy and asked him about his age. He replied, "two days back I was ten years old, but next year I will turn 13." What is his age?


The answer is 11.

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Rohit Sachdeva by Rohit Sachdeva , 30, India

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15 solutions

Ben Farrar
Aug 24, 2014

If today is Jan 1st (lets say 2013), and his B-day is on Dec 31st 2012 (2 days ago he was 10 and now he is 11). Then next year (2014) he will be 13.

2012 Dec 30th - He is 10

2012 Dec 31st - turns 11

2013 Jan 1st - Current day, still 11 [next year will be 2014]

2013 Dec 31st - turns 12

2014 Dec 31st - turns 13

118 Helpful 0 Interesting 0 Brilliant 0 Confused

Thats perfectly correct :)

Rohit Sachdeva - 6 years, 9 months ago

Good solution. Anyway, it must be either 11 or 12. 3 tries given and it's not difficult to get it right.

Hon Ming Rou - 6 years, 9 months ago

2 Days ago I was Ten years old - he is either 10 or 11....... given 365 / 366 days a year.

Dan Evans - 6 years, 8 months ago

simply....... if he was 10 years old 2days back and 13 years old next year then definitely he'll b 11....... there's an age gap of 3years from 2days before he met and the next year so within two days he just can turn up 11.......

Aqeel Asif - 6 years, 9 months ago

awesome solution ^^

Karim Shaféiq - 6 years, 9 months ago

ya its currect.....!

Ritik Patidar - 6 years, 8 months ago

of course u r correct :)

Jenosha Sarah - 6 years, 8 months ago

Nice solution :)

Aditya Narla - 6 years, 8 months ago

Nice explanation! The tricky thing about this problem is that it looks like he will have two birthdays in one year.

Rina Kajitani - 6 years, 7 months ago

Yup its totally correct....

Jatin Rupchandani - 6 years, 9 months ago
Rahul Rahul
Aug 26, 2014

IF Two days back he was 10. Two additional days can turn him 11 only.

114 Helpful 0 Interesting 0 Brilliant 0 Confused

I did it by assuming his b'day 31st dec

Deep Sharma - 6 years, 8 months ago

This is the fact. I thought with New Year and also 29th February for before and after but 10 AND 13 must be a flaw no matter how the story was told. 13 means the answer cannot be 10 for certain despite 10 + 2 + 2 = 14. He must have thought that he was 12 most probably but he had not thought that he could have been 14 next year applying the same rules. 29 February was not the reason for his mistake but only because of New Year. His birthday was 31st December and he talked on 1st January. The only truth must be 11 while story followed made him a wrong thought.

Lu Chee Ket - 6 years, 9 months ago
Praneeth Reddy
Aug 25, 2014

Two days back 10 years that means he is now 11 years. after a year exactly he will be 13 years. coz (11+ 1 ) years two days before this day next year!

so by this day in next year he will be 13

5 Helpful 0 Interesting 0 Brilliant 0 Confused

Praneeth: Thats not how he will be 13.

Look at the problem..it says he will be 13 next year.

30 Dec 2013: 10 years

31 Dec 2013: 11 years (B'Day)

1 Jan 2014: 11 years (Today)

31 Dec 2014: 12 years

31 Dec 2015: 13 years (this is the next year talked about in ques).

Hope this helps.

Rohit Sachdeva - 6 years, 9 months ago

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for example: suppose his birth day is 25 Aug also it works fine! except a leap year! \

may be my explanation is confusing! what you explained is the same thing i wrote in simple way!

Praneeth Reddy - 6 years, 9 months ago

why it should be perticularly dec 30??? what if a leap year comes?

Praneeth Reddy - 6 years, 9 months ago

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Leap year has nothing to do with B'days my friend.

I think what u are counting is exact days..whereas the catch in this question is that we need a sort of extra year to jump from 10 to 13..hence the date 30dec-31dec-1jan.

Considering ur example:

24 august 2013: 10yrs

25 august 2013: turns 11

26 august 2013: still 11(today)

Next year in 2014 he will be 12 at max..he cannot be 13

I think you should re-look the problem

Rohit Sachdeva - 6 years, 9 months ago

i got it wright but i thought by year it meant 365 days exacly so i wos confuzzzzzzzled

Sebastian Hazzan - 6 years, 9 months ago
Manito Solstice
Aug 26, 2014

I figured maybe that the current day was Jan 1st (1-1) That alone tells me that he's eleven since he said that today's date tells you his age.

2 Helpful 0 Interesting 0 Brilliant 0 Confused
Sa Gar
Sep 23, 2014

Forget the whole question and just remember he was 10 , two days ago he can only be 11 not 9 not 12 :D

1 Helpful 0 Interesting 0 Brilliant 0 Confused
Rifath Rahman
Sep 17, 2014

2 days back he was 10,so now he will be 11,simple

1 Helpful 0 Interesting 0 Brilliant 0 Confused
Christie Ann
Mar 23, 2016

They should have asked what his birthday was instead. Would have been trickier that way.

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Neo Umbreon
Mar 10, 2016

wait wait wait wait wait, but if, say, it was July 7, two days ago (day before his birthday), in one year, he would be twelve... and hi birthday would be passed...

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Antonio Basto
Aug 29, 2015

two days back I was ten therefore:

30.......31......1......................................31 same year..............................31 next year 10.......11......11....................................12...................................................13

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Shriya Devadiga
May 8, 2015

it was just trial & error as Avinash said;"2 solutions 3 tries"

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Ashu Singh
Sep 12, 2014

2 days before he was 10 year old.. obviously after 2 days of his birthday .. he can only one year more than before

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Takese Mckenzie
Sep 2, 2014

2 days back he was 10 and in one year he will be 13. Therefore he has to be 11 years old nw

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Pantho Sarker
Sep 1, 2014

His birth date is 1st january

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Aqeel Asif
Aug 31, 2014

simply....... if he was 10 years old 2days back and 13 years old next year then definitely he'll b 11....... there's an age gap of 3years from 2days before he met and the next year so within two days he just can turn up 11.......coz he can't make it more than that :P

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Aymane Kharchouf
Aug 27, 2014

this is not as difficult as it look like, this is no way his age will be more than 11 years in a periode of 2 days , it's impossible !!! the question should be which day is his birthday , that will be difficult

0 Helpful 0 Interesting 0 Brilliant 0 Confused

Yes i guess the more interesting part in the question is its explanation only.

Rohit Sachdeva - 6 years, 9 months ago

if we ignor other part of problm, and take only "next year i will be thirteen,, than this year he is of 12

Saifullah Kohistani - 6 years, 9 months ago

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