Source: NCTM, The
Mathematics Teacher, V. 92, No. 6
(Sept. 1999),

pp. 492-95

Slide No. 12

Arithmetic Solution (continued)

•Teacher: Can both
numbers be even?

•Student: Yes

•Teacher: Are you sure? What do we get, then, when 1 is added to the larger number? Is it even or odd? Could an odd number be the double of the lesser number?