// Numbas version: finer_feedback_settings {"name": "future value - annuity due", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"variable_groups": [], "metadata": {"licence": "Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International", "description": "Financial maths. Future value of an annuity due."}, "variables": {"C": {"group": "Ungrouped variables", "name": "C", "description": "", "definition": "if(period[1]=365,random(1..10),random(20..300#10))", "templateType": "anything"}, "F": {"group": "Ungrouped variables", "name": "F", "description": "", "definition": "(C*period[1]/ipadec)*((1+ipadec/period[1])^(n)-1)*(1+ipadec/period[1])", "templateType": "anything"}, "Frounded": {"group": "Ungrouped variables", "name": "Frounded", "description": "", "definition": "precround(F,2)", "templateType": "anything"}, "ipadec": {"group": "Ungrouped variables", "name": "ipadec", "description": "", "definition": "random(0.02..0.10#0.001)", "templateType": "anything"}, "n": {"group": "Ungrouped variables", "name": "n", "description": "", "definition": "years*period[1]", "templateType": "anything"}, "period": {"group": "Ungrouped variables", "name": "period", "description": "", "definition": "random([random('yearly','annually'),1,'year'],[random('half-yearly','semiannually'),2,'half-year'],['quarterly', 4, 'quarter'],['monthly',12,'month'],['daily', 365,'day'])", "templateType": "anything"}, "ipa": {"group": "Ungrouped variables", "name": "ipa", "description": "", "definition": "ipadec*100", "templateType": "anything"}, "years": {"group": "Ungrouped variables", "name": "years", "description": "", "definition": "random(3..20)", "templateType": "anything"}}, "variablesTest": {"maxRuns": 100, "condition": ""}, "ungrouped_variables": ["years", "period", "ipadec", "ipa", "C", "n", "F", "Frounded"], "parts": [{"sortAnswers": false, "unitTests": [], "marks": 0, "prompt": "

Suppose you are given $\\$\\var{C}$ at the beginning of each {period[2]} for $\\var{years}$ years. If the interest rate is $\\var{ipa}\\%$ per annum compounding {period[0]}, what is this cash flow worth at the end of the $\\var{years}$ years?

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$\\$$ [[0]] (to the nearest cent)

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You are asked to find the future value of an annuity due (since the payments are at the start of each period). Therefore we will use the future value of an annuity due formula

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$\\displaystyle F=\\frac{C}{i}\\left((1+i)^n-1\\right)(1+i)$

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where $F$ is the future value, $C$ is the cash flow per period, $i$ is the interest rate per period, and $n$ is the number of periods.

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In our situation we have,

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$C=\\var{C}$,

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$i=\\frac{\\var{ipa}\\%}{\\var{period[1]}}=\\frac{\\var{ipadec}}{\\var{period[1]}}$, $i=\\var{ipa}\\%=\\var{ipadec}$,

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$n=\\var{years}\\times \\var{period[1]}=\\var{n}$, $n=\\var{n}$,

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and therefore we have

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$\\displaystyle F=\\frac{\\var{C}}{\\left(\\simplify[unitDenominator]{{ipadec}/{period[1]}}\\right)}\\left(\\left(1+\\simplify[unitDenominator]{{ipadec}/{period[1]}}\\right)^\\var{n}-1\\right)\\left(1+\\simplify[unitDenominator]{{ipadec}/{period[1]}}\\right)$

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Calculating this we find 

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$\\begin{align}F&\\approx \\var{F}\\\\&=\\$\\var{Frounded}\\quad \\text{(to the nearest cent)}\\end{align}$

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