// Numbas version: exam_results_page_options {"name": "Simon's copy of Q7 (Calculate the estimate, actual and from these the percentage error)", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"tags": [], "ungrouped_variables": ["num1", "num2", "num3", "num4", "num5", "num7", "num6", "num8", "num9", "num10", "num11", "num12", "num13", "num14", "num15", "num16", "num17", "num18", "num19", "num20", "num21", "ans11", "ans21", "ans31", "ans41", "ans51", "ans61", "ans12", "ans22", "ans32", "ans42", "ans52", "ans62", "ans13", "ans23", "ans33", "ans43", "ans53", "ans63"], "variablesTest": {"maxRuns": 100, "condition": ""}, "functions": {"hun": {"definition": "random(301..599)", "language": "jme", "type": "number", "parameters": []}, "hun1": {"definition": "random(400..600)", "language": "jme", "type": "number", "parameters": []}, "tens": {"definition": "random(35..80#0.01)", "language": "jme", "type": "number", "parameters": []}, "sin": {"definition": "random(3..8#0.01)", "language": "jme", "type": "number", "parameters": []}}, "variable_groups": [], "name": "Simon's copy of Q7 (Calculate the estimate, actual and from these the percentage error)", "statement": "

By rounding each number correct to one significant figure, estimate the answer to each of the problems given below, giving your final estimate to 4 d.p.

\n

Then use your calculator to correctly evaluate the exact calculation to 4 d.p.

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Calculate the percentage error in using the estimate, correct to one decimal place.

\n

 

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ans12)/ ans12)*100", "templateType": "anything", "group": "Ungrouped variables", "description": ""}, "ans33": {"name": "ans33", "definition": "(abs(ans31 - ans32)/ ans32)*100", "templateType": "anything", "group": "Ungrouped variables", "description": ""}, "ans22": {"name": "ans22", "definition": "(num5+num6)/(num7)", "templateType": "anything", "group": "Ungrouped variables", "description": ""}, "num19": {"name": "num19", "definition": "sin()", "templateType": "anything", "group": "Ungrouped variables", "description": ""}, "num12": {"name": "num12", "definition": "sin()", "templateType": "anything", "group": "Ungrouped variables", "description": ""}, "ans61": {"name": "ans61", "definition": "((siground(num19,1)^2)*siground(num20,1))/siground(num21,1)", "templateType": "anything", "group": "Ungrouped variables", "description": ""}, "num10": {"name": "num10", "definition": "random(15..30#0.1 except num8)", "templateType": "anything", "group": "Ungrouped variables", "description": ""}}, "metadata": {"description": "

(Calculate the estimate, actual and from these the percentage error)

\n

rebelmaths

", "licence": "Creative Commons Attribution 4.0 International"}, "advice": "

When rounding off a number to one significant place, round to the left most figure of the number, e.g:

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$367 \\rightarrow 400$,       $38 \\rightarrow 40$,       $71 \\rightarrow 70$

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$3.79 \\rightarrow 4$,       $65.13 \\rightarrow 70$,       $0.0215 \\rightarrow 0.02$

\n

$0.00465 \\rightarrow 0.005$

\n

\n

(a)

\n

\n

Round each number to one significant number:

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$\\var{num1} \\rightarrow \\var{siground(num1,1)}$,        $\\var{num2} \\rightarrow \\var{siground(num2,1)}$

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$\\var{num3} \\rightarrow \\var{siground(num3,1)}$,        $\\var{num4} \\rightarrow \\var{siground(num4,1)}$

\n

\n

So for our approximation we use: 

\n

$\\frac{\\var{siground(num1,1)} \\times \\var{siground(num2,1)}}{\\var{siground(num3,1)} \\times \\var{siground(num4,1)}} = \\var{precround(ans11,4)}$

\n

remembering to give our answer to 4 d.p. as requested.

\n

\n

The exact value is:

\n

$\\frac{(\\var{num1} \\times \\var{num2})}{(\\var{num3} \\times \\var{num4})} = \\var{precround(ans12,4)}$

\n

\n

So our percentage error:

\n

$\\frac{|\\var{precround(ans12,4)} - \\var{precround(ans11,4)}|}{\\var{precround(ans11,4)}} \\times 100 = \\var{precround(ans13,1)}$%

\n

\n

(b),(c),(d) can be completed using a similar method

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$\\frac{\\var{num1} \\times \\var{num2}}{\\var{num3} \\times \\var{num4}}$

\n

Estimate (4dp):       [[0]]

\n

Actual (4dp):          [[1]]

\n

% Error (1dp):        [[2]]%

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$\\frac{\\var{num5} + \\var{num6}}{\\var{num7}}$

\n

Estimate (4dp):       [[0]]

\n

Actual (4dp):          [[1]]

\n

% Error (1dp):        [[2]]%

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$\\frac{\\var{num8} \\times \\var{num9}}{\\var{num10}}$

\n

Estimate (4dp):      [[0]]

\n

Actual (4dp):          [[1]]

\n

% Error (1dp):        [[2]]%

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$\\frac{\\var{num19}^2 \\times \\var{num20}}{\\var{num21}}$

\n

Estimate (4dp):      [[0]]

\n

Actual (4dp):          [[1]]

\n

% Error (1dp):        [[2]]%

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