AI generatedNumberKey Stage 3

Checking the size of a calculator answer

Checking the size of a calculator answer.

  • Make a rough estimate before accepting the calculator result.
  • Check decimal places, brackets and units if the sizes disagree.

Example 1

Estimate the product by rounding each factor down to a whole number. Is the estimate too high or too low?

EstimateBoth positive factors have been rounded down.
EstimateMaking both positive factors smaller makes the product smaller.
84, an underestimate.

Example 2

Estimate the product by rounding each factor down to a whole number. Is the estimate too high or too low?

EstimateBoth positive factors have been rounded down.
EstimateMaking both positive factors smaller makes the product smaller.
110, an underestimate.

Your turn

Question 1

Estimate the product by rounding each factor down to a whole number. Is the estimate too high or too low?

Check answer
EstimateBoth positive factors have been rounded down.
EstimateMaking both positive factors smaller makes the product smaller.
138, an underestimate.
Question 2

Estimate the product by rounding each factor down to a whole number. Is the estimate too high or too low?

Check answer
EstimateBoth positive factors have been rounded down.
EstimateMaking both positive factors smaller makes the product smaller.
168, an underestimate.
Question 3

Estimate the product by rounding each factor down to a whole number. Is the estimate too high or too low?

Check answer
EstimateBoth positive factors have been rounded down.
EstimateMaking both positive factors smaller makes the product smaller.
200, an underestimate.
Question 4

Estimate the product by rounding each factor down to a whole number. Is the estimate too high or too low?

Check answer
EstimateBoth positive factors have been rounded down.
EstimateMaking both positive factors smaller makes the product smaller.
234, an underestimate.
Question 5

Estimate the product by rounding each factor down to a whole number. Is the estimate too high or too low?

Check answer
EstimateBoth positive factors have been rounded down.
EstimateMaking both positive factors smaller makes the product smaller.
270, an underestimate.
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