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SAI INTERNATIONAL SCHOOL
CBSE CURRICULUM
Class: VI
Lesson Note 10.4
SUBJECT : Mathematics
CH: 10 -The other side of zero
SUBTOPIC: Using tokens for addition
In Bela’s Building of Fun, the lift attendant is bored. To entertain himself, he keeps a box
containing lots of positive (red) and negative (green) tokens. Each time he presses the ‘+’
button, he takes a positive token from the box and puts it in his pocket. Similarly, each time
he presses the ‘–’ button, he takes a negative token and puts it in his pocket. He starts on the
ground floor (Floor 0) with an empty pocket. After one hour, he checks his pocket and finds 5
positive and 3 negative tokens. On which floor is he now? He must have pressed ‘+’ five times
and ‘–’ 3 times and (+5)+(–3)=+2. So, he is at Floor +2 now. Here is another way to do the
calculation.
A positive token and a negative token cancel each other, because the value of this pair of
tokens together is zero. These two tokens in his pocket meant that he pressed ‘+’ once and
‘–’ once, respectively, and these cancel each other. We say that a positive and a negative
