AQA · Mathematics · 8300
GCSE Maths: Limits of accuracy
Geometry & Measures · AQA GCSE Maths (8300). Cards are generated from the Corbettmaths textbook exercise and practice questions for Limits of accuracy (Corbettmaths Video 183), and every card links back to the exact page it came from. Practice tests are drawn from this deck’s own cards. Source material © Corbettmaths — used with attribution.
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What is the lower bound of a value rounded to the nearest whole unit?
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The original value minus half the unit of measurement. For example, for 4g to the nearest gram, the lower bound is 3.5g.
What is the upper bound of a value rounded to the nearest whole unit?
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The original value plus half the unit of measurement. For example, for 4g to the nearest gram, the upper bound is 4.5g.
For a value measured to the nearest 10 units, the error margin is ?.
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±5 units
For 50kg measured to the nearest 10kg, what are the lower and upper bounds?
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Lower bound: 45kg; Upper bound: 55kg
For a value measured to the nearest 0.1 units, what is the error margin?
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±0.05 units. Half of 0.1 is 0.05.
For 150,000,000 km correct to 2 significant figures, what is the lower bound?
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145,000,000 km. The rounding unit for 2 s.f. is 5,000,000, so subtract half of that.
When finding the maximum total of two rounded values, do you add upper bounds or lower bounds?
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Upper bounds. To maximize the total, use the largest possible value for each.
When finding the minimum difference between two rounded values, which bounds do you use?
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Lower bound of the larger value minus upper bound of the smaller value. This minimizes the gap.
When calculating the smallest possible mean from measurements given to one decimal place, what version of each measurement should you use?
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The lower bound of each measurement. This minimizes the sum and therefore the mean.
When calculating the greatest possible range from measurements, which bounds should you use?
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Subtract the lower bound of the smallest value from the upper bound of the largest value. This maximizes the difference.
When calculating the lower bound of an area (length × width), which bounds of the measurements should you use?
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Multiply the lower bounds of both dimensions. When multiplying, use lower bounds to get the minimum possible area.
When calculating the lower bound of a division m/t, which bounds should you use?
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Divide the lower bound of the numerator by the upper bound of the denominator. This minimizes the quotient.
When calculating upper bound for speed (distance/time), which bounds should you use?
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Divide the upper bound of distance by the lower bound of time. This maximizes the speed.
When rearranging A = πrl to find l and calculating the upper bound for l, which bounds should you use?
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Divide the upper bound of A by the lower bounds of π and r. Since l = A/(πr), maximize A and minimize the denominator.
If a price after an 18% reduction is £6200, what operation finds the original price?
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Divide by 0.82 (since 100% - 18% = 82%). If final price is 82% of original, then original = final ÷ 0.82.
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