Stage: 1 Short Challenge Level: 
I am less than 25.
My ones digit is twice my tens digit.
My digits add up to an even number.
What am I?
Interactivities. Factors and multiples. Digit cards. Multiplication & division. Working systematically. Comparing and Ordering numbers. Generalising. Odd and even numbers. Addition & subtraction. Place value.
Published February 2000,January 2009.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk