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Sonia uses the letter b for the number of books in a carton. Rahul uses the letter for the very same thing. Whose choice is correct?

Class 6AlgebraAlgebra
  • ASonia only, because the letter must match the first letter of the word.
  • BRahul only, because is the one letter allowed for an unknown.
  • CNeither, because a variable must always be written as n.
  • DBoth, because any letter may stand for the number as long as you say what it means.

Step-by-Step Solution

A variable is just a placeholder, so the letter itself carries no meaning — b, , n or t all work provided you state what the letter counts. Choosing a helpful letter is a convenience, never a rule.
Answer: D) Both, because any letter may stand for the number as long as you say what it means.

Key idea: Why letters?

Imagine you want to describe 'a number doubled, plus three'. Without algebra you would have to make a list: ; ; ; … forever. With a letter — say for 'the number' — the whole list becomes one short expression: ****. Pick any value of and you get the right answer. The letter is shorthand for 'whatever number we're talking about'.

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