Maths question.

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  • arciere
    arciere Posts: 1,354 Forumite
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    Chino wrote: »
    Why would you do that when you know that this will lead to a recurring decimal in the answer?
    I did a similar thing because it can apply to different situations (i.e. 1 hour and 13 minutes)
  • jackieblack
    jackieblack Posts: 10,316 Forumite
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    Chino wrote: »
    Why would you do that when you know that this will lead to a recurring decimal in the answer?

    I agree
    Much simpler to do 35/70 first then multiply by 60, especially if not using a calculator
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  • debitcardmayhem
    debitcardmayhem Posts: 11,858 Forumite
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    arciere wrote: »
    10 minutes equal to approx 0.167 hours (1h divided by 60 times 10). Add that to the 1 hour, you get 1.167h. So the person travelled 35km/1.167h.
    If you need km/h, you just divide 35 by 1.167.

    Unless I got it wrong.
    Not close enough B-

    1 Hour is 6/7 of 70 minutes thus 35*6/7 = 30 no approximation just pure maths
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  • neilmcl
    neilmcl Posts: 19,460 Forumite
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    jackieblack wrote: »
    I agree
    Much simpler to do 35/70 first then multiply by 60, especially if not using a calculator
    +1, this is how you'd be expecting a 11 year old to be working it out.
  • 18cc
    18cc Posts: 2,120 Forumite
    well it is 35km in 70 mins ie 5km every 10 mins ie 30 km per 60 mins ie 30 km per hour
  • esuhl
    esuhl Posts: 9,409 Forumite
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    This is how I'd explain it (if another example helps):

    You want to find the speed, and you know the distance and time, so you can use the formula:

    speed = distance / time

    Using the figures you have:

    speed = 35km / 1h10m

    It's easier to have time in a single unit (rather than a non-decimal combination of hours and minutes). To avoid unnecessary decimal points and fractions, it makes sense to use minutes. So:

    speed = 35km / 70mins

    We want the distance-per-hour, not per-70-minutes. The easiest way to do this is to find the distance-per-minute and then multiply by 60 to get distance-per-hour. So:

    speed = (35/70)km / (70/70)mins

    Simplify the fractions to:

    speed = (1/2)km / 1min

    And multiply by 60:

    speed = 30km / 60min

    Which is:

    speed = 30km/h
  • Cornucopia
    Cornucopia Posts: 16,154 Forumite
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    If the question doesn't specify the units for showing the speed, then I think I'd probably go with:-

    35 km / 70 mins = 0.5 km/min.
  • G42
    G42 Posts: 198 Forumite
    If a person travels 35 km in 1 hour 10 mins. what is her average speed?

    The question is incomplete. The actual question is - If a person travels 35 km in 1 hour 10 mins what is her average speed in km per hour?

    This can now be simplified into - If a person travels 35 km in 70 minutes how far does she travel in 60 minutes?

    Answer – Find out how many km she travels in 1 hour (60 mins). In other words km per hour.

    35 (km) divided by 70 (mins) gives distance travelled in 1 minute
    Multiplied by 60 (mins) gives distance travelled in 60 minutes (1hr)

    Calculation
    = 35 divided by 70 then multiplied by 60
    = 35/7*6
    = 30
  • TheCyclingProgrammer
    TheCyclingProgrammer Posts: 3,702 Forumite
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    Undefined as you don’t specify what units you want the answer in, but assuming you want kilometres per hour, the answer is 30 kph. 1 hour and 10 minutes as a fraction is 1 and 1/6 of an hour, or 7/6, so to find out the distance travelled in an hour you need to do 35 * 6/7, Which is 30.

    Alternatively you can consider that they travelled 35 km in 70 minutes, which is 0.5km per minute and go from there.
  • TheCyclingProgrammer
    TheCyclingProgrammer Posts: 3,702 Forumite
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    arciere wrote: »
    He travels 35km/1.167h, that makes it 29.99km/h

    The answer is 30. You’ve lost precision because you’ve rounded 1/6th to the nearest 100th. Sometimes it’s easier to just use fractions.
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