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[], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

A two-stroke fuel is mixed using the fuel to oil ratio {twostrokefuel}:1.

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This is equivalent to the ratio  [[0]] : {twostrokeoil}.

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These questions are similar to equivalent fractions. To create an equivalent ratio, you need to multiply (or divide) by the same number on both sides.

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For example,  suppose your ratio is $4:5$ and you are asked to find an equivalent ratio that looks like $?:30$. To get from a 5 to a 30 we can multiply by 6, but to keep the ratio equivalent we need to do the same to the other side of the ratio. So we multiply 4 by 6 and get 24 and we can say the ratios $4:5$ and $24:30$ are equivalent.

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As a more complicated example, suppose we need to find an equivalent ratio of $4:5$ in the form $31:?$. We need to get from a 4 to a 31 by multiplying or dividing. The easiest way to do this is probably to divide by 4 and then multiply by 31 (note, this is the same as multiplying by $\\frac{31}{4}$). We need to do the same thing to the other side of the ratio. So we multiply 5 by $\\frac{31}{4}$ and get $\\frac{155}{4}$ and we can say the ratios $4:5$ and $31:\\frac{155}{4}$ are equivalent.

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A fixed gear bike is set up in such a way that one revolution of the pedals moves the bike {onedistance} metres. To ride the bike {requireddistance} metres how many revolutions of the pedals are required? 

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[[0]] revolutions.

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Note: If the answer has many decimal places leave your answer as a fraction (using / as the fraction bar) so that your answer is exact (and not an approximation/rounded-answer)

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These questions are similar to equivalent fractions. To create an equivalent ratio, you need to multiply (or divide) by the same number on both sides.

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\n
\n

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For example,  suppose your ratio is $4:5$ and you are asked to find an equivalent ratio that looks like $?:30$. To get from a 5 to a 30 we can multiply by 6, but to keep the ratio equivalent we need to do the same to the other side of the ratio. So we multiply 4 by 6 and get 24 and we can say the ratios $4:5$ and $24:30$ are equivalent.

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As a more complicated example, suppose we need to find an equivalent ratio of $4:5$ in the form $31:?$. We need to get from a 4 to a 31 by multiplying or dividing. The easiest way to do this is probably to divide by 4 and then multiply by 31 (note, this is the same as multiplying by $\\frac{31}{4}$). We need to do the same thing to the other side of the ratio. So we multiply 5 by $\\frac{31}{4}$ and get $\\frac{155}{4}$ and we can say the ratios $4:5$ and $31:\\frac{155}{4}$ are equivalent.

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A cordial is mixed using the syrup to water ratio {cordialratio[0]}:{cordialratio[1]}. You need to make {totalcordial} litres. How many litres of syrup do you need?

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 [[0]] L

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Note: If the answer has many decimal places leave your answer as a fraction (using / as the fraction bar) so that your answer is exact (and not an approximation/rounded-answer)

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Determine the total number of parts used in the ratio. Find what one part corresponds to and then multiply by the required number of parts.

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For example, suppose you need to divide 490 kg into the ratio 2:5. The ratio has 7 parts (2+5). One part corresponds to $\\frac{490}{7}=70$ kg. This means 2 parts corresponds to $2\\times 70=140$ kg, and 5 parts corresponds to $5\\times 70=350$ kg. Therefore, 490 kg divided into the ratio 2:5 is 140 kg : 350 kg. 

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Three people split \\${totaldollars} amongst themselves in the ratio {part1}:{part2}:{part3}. How much money does the {position[0]} person get? 

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\\$ [[0]] (to the nearest cent)

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Determine the total number of parts used in the ratio. Find what one part corresponds to and then multiply by the required number of parts.

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For example, suppose you need to divide 800 kg into the ratio 2:5:1. The ratio has 8 parts (2+5+1). One part corresponds to $\\frac{800}{8}=100$ kg. This means 2 parts corresponds to $2\\times 100=200$ kg and 5 parts corresponds to $5\\times 100=500$ kg. Therefore, 800 kg divided into the ratio 2:5:1 is 200 kg : 500 kg : 100 kg. 

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Unit rates and converting rates.

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plural, singular, object

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{person} {thing[0]} {number} {thing[2]} per {integer} {unit}s. This is equivalent to {thing[1]} [[0]] {thing[2]} per {unit}.

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Note: If the answer has many decimal places leave your answer as a fraction (using / as the fraction bar) so that your answer is exact (and not an approximation/rounded-answer)

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The word 'per' can be replaced with the operation of division.

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These questions are very similar to equivalent fractions.

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Suppose you are told 'Daniel eats 61 berries per 3 hours'. The following three methods are equivalent but might appear different.

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  1. We are given 61 berries / 3 hours. Divide both sides of the rate by 3 (so that we are dealing with 'per hour' not 'per 3 hours'). This gives 61/3 berries/hour.
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  3. \\[\\text{61 berries/3 hours}=\\frac{61\\text{ berries}}{3 \\text{ hours}}=\\frac{61}{3}\\frac{\\text{berries}}{\\text{hour}}=\\frac{61}{3} \\,\\text{berries/hour}.\\]
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  5. \\[\\text{61 berries/3 hours}=\\frac{61\\text{ berries}}{3 \\text{ hours}}=\\frac{61\\text{ berries }\\div 3}{3 \\text{ hours }\\div 3}=\\frac{61\\div 3\\text{ berries }}{1 \\text{ hour }}=\\frac{61}{3} \\,\\text{berries/hour}.\\]
  6. \n
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A {vehicle} travels {distance} km per {amount} L of petrol.  

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How many kilometres can be travelled by using {niceamount} L? [[1]] km

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How many litres of petrol are needed to travel {nicedistance} km? [[0]] L

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Note: If the answer has many decimal places leave your answer as a fraction (using / as the fraction bar) so that your answer is exact (and not an approximation/rounded-answer)

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Just like a fraction, we can multiply or divide both sides of the rate by any number (except 0).

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Suppose you have 'a motorbike travels 245 km per 13 L of petrol'. Note, this can be written as 245 km / 13 L.

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To determine kilometres per 20 L, first determine how many kilometres per 1 L, and then multiply by 20. That is, 

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245 km / 13  L  = $\\frac{345}{13}$ km/L =  $\\frac{345}{13}\\times 20$ km / 20 L.

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To determine litres per 50 km, first determine how many litres per 1 km, and then multiply by 50. That is,

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245 km / 13 L = 1 km / $\\frac{13}{245}$ L = 50 km / $\\frac{13}{245}\\times 50$ L.

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Note, 245 km per 13 L could also be written as 13 L / 245 km. It might be simpler to do the second question this way:

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 To determine litres per 50 km, first determine how many litres per 1 km, and then multiply by 50. That is,

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13 L / 245 km = $\\frac{13}{245}$ L / km = $\\frac{13}{245}\\times 50$ L / 50 km.

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A rate of {num1} {firstunit[0]}s / {num2} {secondunit[0]}s is equivalent to [[0]] {firstunit[1]}s / {secondunit[1]}.

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Note: If the answer has many decimal places leave your answer as a fraction (using / as the fraction bar) so that your answer is exact (and not an approximation/rounded-answer)

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Just like a fraction, we can multiply or divide both sides of the rate by any number (except 0). Do one thing at a time to avoid making a mistake.

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For example, suppose we need to convert 24 milliseconds / 4 litres into an equivalent rate in minutes / kilolitre. We need to do the following steps:

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    \n
  1. convert milliseconds to minutes,
  2. \n
  3. convert litres to kilolitres,
  4. \n
  5. make it per kilolitre. 
  6. \n
\n

\n
\n

\n
    \n
  1. There are 60,000 milliseconds in a minute so to convert from millisecond to minutes we divide the milliseconds by 60,000. We now have 0.0004 minutes / 4 litres.
  2. \n
  3. There are 1,000 litres in a kilolitre so to convert from litres to kilolitres, you need to divide the litres by 1,000. We now have 0.0004 minutes / 0.004 litres. 
  4. \n
  5. To make it per litre we recall that 0.0004 minutes / 0.004 litres is equivalent to 0.0004/0.004 minutes / litre (this is the same as dividing both sides by 0.004). 
  6. \n
\n

So our final answer is 0.1 minutes / litre.

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