Approximate rational calculations
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Estimate 49% of $120 using the nearby familiar fraction one-half. What is the estimate?
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Answer: $60.00
- 49% is close to 50%, which is one-half.
- Half of 120 is 60. The estimate is slightly above the exact 49% result.
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Curriculum reference
Victorian Curriculum F–10 Version 2.0
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Choose an estimate accurate enough for the purpose.
Read the official VCAA curriculum description (VC2M6N08)
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- Supported by the guided activity; selecting an MCQ does not demonstrate this action.
- VC2M6N08-C01Approximate 49% by one-half, 26% by one-quarter or 0.34 by one-third when that suits the purpose. State the chosen approximation so an estimate is not confused with an exact answer.
- VC2M6N08-C02Nearby multiples can make equal-sharing or repeated-cost calculations easier. Track whether rounding moved each input up or down, because that helps explain whether the result is an overestimate or underestimate.
- VC2M6N08-C03Familiar fractions and percentages can place an answer between useful limits. An underestimate is not enough to prove a purchase fits a strict budget. Compare approximation errors on the same whole and check exact values when the margin matters.
- VC2M6N08-C04Choosing and justifying estimation strategies for rational numbers and percentages.
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- D01Use familiar benchmarksApproximate 49% by one-half, 26% by one-quarter or 0.34 by one-third when that suits the purpose. State the chosen approximation so an estimate is not confused with an exact answer.
- D02Choose compatible numbersNearby multiples can make equal-sharing or repeated-cost calculations easier. Track whether rounding moved each input up or down, because that helps explain whether the result is an overestimate or underestimate.
- D03Use bounds for decisionsFamiliar fractions and percentages can place an answer between useful limits. An underestimate is not enough to prove a purchase fits a strict budget. Compare approximation errors on the same whole and check exact values when the margin matters.