Arithmetic Expressions | A

Question 1

Context: In an expression having two terms, swapping them does not change the value:

Term 1+Term 2=Term 2+Term 1\text{Term 1} + \text{Term 2} = \text{Term 2} + \text{Term 1}

Q. Can you explain why this is happening using the Token Model of integers that we saw in the Class 6 textbook of mathematics?

Question diagram 1
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Solution
Understand the Question
  • In the Token Model, an integer is represented by a set of tokens (for example, negative numbers are represented by negative tokens).
  • Adding two terms means combining their collections of tokens into one single group.
  • The total number and nature of tokens collected in the group remain the same regardless of which group of tokens is placed first.
  • Thus, Term 1+Term 2=Term 2+Term 1\text{Term 1} + \text{Term 2} = \text{Term 2} + \text{Term 1} holds true because grouping is independent of order.

Step 1 · Evaluate Term 1 + Term 2

Let Term 1=3\text{Term 1} = -3 (33 negative tokens) and Term 2=2\text{Term 2} = -2 (22 negative tokens).Diagram 1

Combining Term 1\text{Term 1} and Term 2\text{Term 2}:

(3)+(2)=3 negative tokens+2 negative tokens=5 negative tokens=5\begin{aligned} (-3) + (-2) &= \text{3 negative tokens} + \text{2 negative tokens} \\[0.6em] &= \text{5 negative tokens} = -5 \end{aligned}

Step 2 · Evaluate Term 2 + Term 1

Now, reverse the order and combine Term 2\text{Term 2} and Term 1\text{Term 1}:Diagram 2

(2)+(3)=2 negative tokens+3 negative tokens=5 negative tokens=5\begin{aligned} (-2) + (-3) &= \text{2 negative tokens} + \text{3 negative tokens} \\[0.6em] &= \text{5 negative tokens} = -5 \end{aligned}

Since both orders result in 55 negative tokens (5-5), swapping the terms does not change the value.

Answer

Yes. Using the Token Model, combining 33 negative tokens and 22 negative tokens in any order always results in 55 negative tokens (5-5), proving that Term 1+Term 2=Term 2+Term 1\text{Term 1} + \text{Term 2} = \text{Term 2} + \text{Term 1}.

Common Mistakes
  • Order Confusion: Thinking that placing tokens in a different sequence alters the total count or sign of the resulting group.
  • Sign Mixing: Confusing positive and negative tokens when combining terms of the same sign.

More questions in A

Q1

Context: In an expression having two terms, swapping them does not change the value:

Term 1+Term 2=Term 2+Term 1\text{Term 1} + \text{Term 2} = \text{Term 2} + \text{Term 1}

Q. Can you explain why this is happening using the Token Model of integers that we saw in the Class 6 textbook of mathematics?

Q3

Context: Let us consider the expression (7)+10+(11)(-7) + 10 + (-11) again. What happens when we change the order and add 7-7 and 11-11 first, and then add this sum to 1010? Will we get the same sum as before? We see that adding the terms of the expression (7)+10+(11)(-7) + 10 + (-11) in any order gives the same sum of 8-8.

Q. Does adding the terms of an expression in any order give the same value? Take some more expressions and check. Consider expressions with more than 3 terms also.

Q4

Context: Does adding the terms of an expression in any order give the same value? Take some more expressions and check. Consider expressions with more than 33 terms also.

Q. Can you explain why this is happening using the Token Model of integers that we saw in the Class 6 textbook of mathematics?

Q5

What happens to the value of an expression if we increase or decrease the value of one of its terms?

Some expressions are given in following three columns. In each column, one or more terms are changed from the first expression. Go through the example (in the first column) and fill the blanks, doing as little computation as possible.

Q6

Expression Engineer!

Using three 3's along with the four operations (addition, subtraction, multiplication, and division) and brackets as needed we can create several expressions. For example, 3+33=2\dfrac{3 + 3}{3} = 2, 3+33=33 + 3 - 3 = 3, 3×3+3=123 \times 3 + 3 = 12, and so on.

  • Using four 4's, create expressions to get all values from 1 to 20.
  • Using the numbers 1, 2, 3, 4, and 5 exactly once in any order get as many values as possible between 10-10 and +10+10.
  • Using the numbers 0 to 9 exactly once in any order, make an expression with a value 100.
  • What other similar interesting questions can you ask?
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