Learn to translate English phrases into mathematical expressions using letter-numbers (variables).
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Introduce Shabnam and Aftab age problem.
When Aftab's age is 10 years, Shabnam's age will be 13 years.
Now Aftab's age is 18 years, what will Shabnam's age be?
Comparing word phrases to algebraic symbols side-by-side.
Replacing specific numbers with a letter helps us create a general expression that works for any age.
Define letter-numbers and algebraic expressions.
Letters such as and that are used to represent numbers are called letter-numbers. They allow us to write mathematical relations in a shorthand, concise form.
Table of common word-to-math translations.
Worked example from page 83.
Ketaki prepares and supplies coconut-jaggery laddus. The price of a coconut is ₹35 and the price of 1 kg jaggery is ₹60.
How much should she pay if she buys specific amounts, and what is the general expression for any amount?
Faded example building expressions for currency notes.
Krithika has notes of ₹100, ₹20, and ₹5. For 3, 5, and 6 notes respectively, the total amount is calculated as . For 8 notes of ₹100, 4 notes of ₹20, and notes of ₹5, the expression is . Generalizing this, if she has notes of ₹100, notes of ₹20, and notes of ₹5, the complete algebraic expression for her total amount is .
Multiple choice expression formulation.
Venkatalakshmi owns a flour mill. It takes 10 seconds for the roller mill to start running. Once it is running, each kg of grain takes 8 seconds to grind into powder. Assuming the machine is off initially, which expression describes the time taken to completely grind kg of grain?