// Numbas version: exam_results_page_options {"name": "Consumer Arithmetic - Simple Interest", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"preamble": {"js": "", "css": ""}, "metadata": {"licence": "Creative Commons Attribution 4.0 International", "description": "

Calculate the interest accrued in a savings account, given the initial balance and annual interest rate.

"}, "rulesets": {}, "statement": "

Suppose you put \\${money} into a savings account exactly {years} years ago and you haven't touched the money since. The simple interest rate on the account is {perc2}% per year.

", "variables": {"years": {"group": "Ungrouped variables", "definition": "random(2..6)", "description": "", "templateType": "anything", "name": "years"}, "money": {"group": "Ungrouped variables", "definition": "random(100..5000 #100)", "description": "", "templateType": "anything", "name": "money"}, "perc2": {"group": "Ungrouped variables", "definition": "random(0..2.5 #0.05)", "description": "", "templateType": "anything", "name": "perc2"}}, "variablesTest": {"maxRuns": 100, "condition": ""}, "name": "Consumer Arithmetic - Simple Interest", "functions": {}, "advice": "

This is simple interest, which means the amount added each year is a percentage of the original amount. The amount we add is fixed for all {years} years.

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First, we work out the amount of interest for one year:

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\\begin{align}
\\var{perc2} \\text{% of } \\var{money} &= \\frac{\\var{perc2}}{100} \\times \\var{money} \\\\
&= \\var{perc2/100} \\times \\var{money} \\\\
&= £\\var{dpformat(perc2/100*money,2)} \\text{.} 
\\end{align}

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The money has been in the account for {years} years, so we multiply $£\\var{dpformat(perc2/100*money,2)}$ by $\\var{years}$.

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\\[ £\\var{dpformat(perc2/100*money,2)} \\times \\var{years} = £\\var{dpformat(perc2/100*money*years,2)} \\text{.} \\]

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Adding this to the original balance:

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\\[ £\\var{money} + £\\var{dpformat(perc2/100*money*years,2)}  = £\\var{dpformat(perc2/100*money*years + money,2)} \\text{.} \\]

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This is the amount we would get if we withdrew the whole savings balance today.

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 If you were to withdraw the money from this account now, how much would you have?

\n

$ [[0]]

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