// Numbas version: finer_feedback_settings {"name": "Using formulas", "metadata": {"description": "
A quick practice set of problems for education students to take in preparation for their numeracy test.
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\nIf you are unsure of how to do a question, click on Show steps to see the full working. Then, once you understand how to do the question, click on Try another question like this one to start again.
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\n$\\displaystyle \\text{drip rate (dpm)}=\\frac{\\text{volume (mL)} \\times \\text{drop factor (drops/mL)}}{\\text{time (hr)}\\times \\text{60 (min/hr)}}$
\nIf the volume is $\\var{v}$ mL, the duration is $\\var{h}$ hours and there are $\\var{f}$ drops/mL, then the drip rate is
\n[[0]] (drops/min) to the nearest whole number
", "sortAnswers": false, "extendBaseMarkingAlgorithm": true, "showFeedbackIcon": true, "useCustomName": false, "steps": [{"prompt": "We take the formula
\n$\\displaystyle \\text{drip rate (dpm)}=\\frac{\\text{volume (mL)} \\times \\text{drop factor (drops/mL)}}{\\text{time (hr)}\\times \\text{60 (min/hr)}}$
\nand substitute the following
\n$\\text{volume}=\\var{v}$,
\n$\\text{drop factor}= \\var{f}$,
\n$\\text{time}= \\var{h}$
\nso that we have
\n$\\displaystyle \\text{drip rate (dpm)}=\\frac{\\var{v} \\times \\var{f}}{\\var{h}\\times 60}$
\nUsing a calculator we would find
\n$\\begin{align}\\text{drip rate (dpm)}&\\approx\\var{drip} \\text{ dpm}\\\\&=\\var{driprounded}\\text{ dpm (to the nearest whole number)}\\end{align}$
\n\nWithout a calculator, you could do this calculation by
\nHowever, it is often best to look for common factors and cancel them before the multiplication and division. That is, given:
\n$\\displaystyle \\text{drip rate (dpm)}=\\frac{\\var{v} \\times \\var{f}}{\\var{h}\\times 60}$
\nI would look for a common factor between $\\var{v}$ and $\\var{h}$. But, alas, there isn't one. There is a common factor of $\\var{cfvh}$, so I'd remove this from the top and bottom and be left with
\n$\\displaystyle \\text{drip rate (dpm)}=\\frac{\\var{v'} \\times \\var{f}}{\\var{h'}\\times 60}$
\nThen I'd look for a common factor between $\\var{v'}$ and $\\var{60}$. But, alas, there isn't one. There is a common factor of $\\var{cfvs}$, so I'd remove that from the top and bottom and be left with
\n$\\displaystyle \\text{drip rate (dpm)}=\\frac{\\var{v''} \\times \\var{f}}{\\var{h'}\\times \\var{s'}}$
\nThen I'd look for a common factor between $\\var{f}$ and $\\var{h'}$. But, alas, there isn't one. There is a common factor of $\\var{cffh'}$, so I'd remove that from the top and bottom and be left with
\n$\\displaystyle \\text{drip rate (dpm)}=\\frac{\\var{v''} \\times \\var{f'}}{\\var{h''}\\times \\var{s'}}$
\nThen I'd look for a common factor between $\\var{f'}$ and $\\var{s'}$. But, alas, there isn't one. There is a common factor of $\\var{cffs'}$, so I'd remove that from the top and the bottom and be left with
\n$\\displaystyle \\text{drip rate (dpm)}=\\frac{\\var{v''} \\times \\var{f''}}{\\var{h''}\\times \\var{s''}}$
\n\nSo, after all that, I only need to do
\nTwo common formulas used to convert between the units of temperature Celsius (C) and Fahrenheit (F) are:
\n$F=\\frac{9}{5}C+32\\quad$ and $\\quad C=\\frac{5}{9}(F-32)$
\n(These are actually equivalent equations, each can be rearranged into the other)
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\n$\\var{from_temp} ^\\circ\\var{from}=$[[0]] $^\\circ\\var{to}$ (to the nearest whole $^\\circ\\var{to}$)
", "stepsPenalty": "1", "steps": [{"type": "information", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "Since we know the temperature in Celsius but want it in Fahrenheit the easiest formula to use would be
\n$F=\\frac{9}{5}C+32$.
\nRecall $\\frac{9}{5}C$ means $\\frac{9}{5}\\times C$ or $\\frac{9}{5}$ of $C$.
\nSubstituting (replacing) $C$ with what it is worth ($\\var{from_temp}$) gives
\n$F=\\frac{9}{5}\\times\\var{from_temp}+32$.
\nFollowing the order of operations we find:
\n$\\begin{align*}F&=\\frac{9}{5}\\times\\var{from_temp}+32\\\\&=\\var{9/5*from_temp}+32\\\\&=\\var{to_temp}\\end{align*}$.
\nWe round to the nearest whole number (if necessary) to get
\n$\\var{to_temp_approx}^\\circ\\var{to}$.
\nSince we know the temperature in Fahrenheit but want it in Celsius the easiest formula to use would be
\n$C=\\frac{5}{9}(F-32)$.
\nRecall $\\frac{5}{9}$ in front of the bracket means $\\frac{5}{9}$ times the result of the bracket or $\\frac{5}{9}$ of the result of the bracket.
\nSubstituting (replacing) $F$ with what it is worth ($\\var{from_temp}$) gives
\n$C=\\frac{5}{9}(\\var{from_temp}-32)$.
\nFollowing the order of operations we find:
\n$\\begin{align*}C&=\\frac{5}{9}\\times(\\var{from_temp}-32)\\\\&=\\frac{5}{9}\\times \\var{from_temp-32}\\\\&=\\var[fractionNumbers]{to_temp}\\end{align*}$.
\nWe round to the nearest whole number (if necessary) to get
\n$\\var{to_temp_approx}^\\circ\\var{to}$.
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", "licence": "Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International"}, "statement": "Calculate the following with the use of a calculator.
", "advice": "", "rulesets": {}, "variables": {"upordown": {"name": "upordown", "group": "Ungrouped variables", "definition": "if(bmi6dec>bmi,\"down\",if(bmi6decThe formula for BMI (Body Mass Index) is
\n\\[\\text{BMI}=\\frac{\\text{mass (kg)}}{\\text{height (m)}^2}.\\]
\nThe patient's BMI to two decimal places is [[0]].
", "stepsPenalty": "1", "steps": [{"type": "information", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "The equation for BMI is
\n\\[\\text{BMI}=\\frac{\\text{mass (kg)}}{\\text{height (m)}^2}\\]
\nNotice the units in the formula are kilograms and metres. We convert the $\\var{height}$ cm into metres by moving the decimal point twice to the left to get $\\var{height/100}$ m.
\nUsing a scientific calculator you can type in \\[\\var{mass}\\div \\var{height/100}^2\\] or by using the fraction button you may be able to type in \\[\\frac{\\var{mass}}{\\var{height/100}^2}\\] and it will give you something like $\\var{bmi6dec}$ which you need to round {upordown} to two decimal places and get $\\var{bmi}$ $\\var{bmi}0$ $\\var{bmi}.00$
\n\n\nA few things to remark:
\nsignificant figures of velocity
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\n", "stepsPenalty": "1", "steps": [{"type": "information", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "
Be mindful of the order of operations and negatives when evaluating expressions.
\n\n
Substituting $a=\\var{aval}$, $b=\\var{bval}$ and $c=\\var{cval}$ into $b^2-4ac$ gives
\n\\[(\\var{bval})^2-4(\\var{aval})(\\var{cval})=\\simplify[basic]{{bval^2}-4{aval}{cval}}=\\simplify[basic]{{bval^2}+{-4*aval*cval}}=\\var{disans}.\\]
\nSubstituting $x=\\var{xval}$ and $y=\\var{yval}$ into $\\simplify{(x-{aval})^2+(y-{cval})^2}$ gives
\n\\[\\simplify[basic]{({xval}-{aval})^2+({yval}-{cval})^2}=(\\var{xval-aval})^2+(\\var{yval-cval})^2=\\var{(xval-aval)^2}+\\var{(yval-cval)^2}=\\var{cirans}.\\]
\nSubstituting $m_0=\\var{m0}$, $v=\\var{v_sig_figs}\\times 10^8$ and $c=3\\times 10^8$ into $m=\\dfrac{m_0}{\\sqrt{1-\\frac{v^2}{c^2}}}$ gives
\n\\[m=\\dfrac{\\var{m0}}{\\sqrt{1-\\frac{(\\var{v_sig_figs}\\times 10^8)^2}{(3 \\times 10^8)^2}}}=\\var{mans} \\quad\\text{ (to two decimal places).}\\]
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