Copyright © University of Cambridge. All rights reserved.
'Weekly Problem 17 - 2006' printed from http://nrich.maths.org/
Granny says "I am $84$ years old - not counting my Sundays". How old is she really?
Granny is calculating her age as if every week has six days not seven - she is therefore saying she is younger than she is because (for example) Granny is working on $6$ weeks only having $36$ not $42$ days but a year is still $365$ days long.
If you liked this problem, here is an NRICH task
which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.View the previous week's solution