When Big Gets Smaller

Using Number Properties

Problem: “Nara buys 0.345 kilograms of chocolates, which costs $9.78 per kilogram. Work out the approximate cost. Is the answer less than or more than $9.78?”

(Possible answer: 0.345 x 9.78 ≈ 3 tenths of 10 = 3. So the answer is less than $9.78.)

Use the calculator to find the cost of the chocolates and round sensibly.)

(Answer: 0.345 x 9.78 = 3.3741 = $3.37 to the nearest cent.)

Examples: Worksheet (Material Master 8–15).

Understanding Number Properties:

How will you work out whether the answers to problems like 56.8 x 1.088 or 0.000123 x 567 get bigger or smaller?

Understanding Number Properties:

 z x y is always smaller than z when y is ... (Answer: less than 1).

z x y is always bigger than z when y is ... (Answer: greater than 1).