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• Do you have a friend or a sibling

• that's always competing with you

• to see who's the fastest?

• Our alien friends Bleebop and Mark

• are having the same debate

• with their custom-built rockets,

• to be the judge of a space race to their moon.

• The only problem is that they are starting

• from different asteroids.

• Bleebop is on an asteroid 240 miles from the moon,

• and Mark is on one 150 miles away.

• Don't worry, it's not rocket science.

• Solving this equation is as simple as DIRT.

• We can decide who the winner is

• using the D=RT formula, or DIRT.

• This stands for distance equals rate times time.

• In the case of Bleebop and Mark,

• we will only know the distance they traveled

• and the time it took for them

• to get to the finish line.

• It'll be up to us to find the rate

• and who is faster.

• Let's turn to the race now

• and see what information we get.

• Three,

• two,

• one,

• blast off!

• Bleebop and Mark's rockets go zipping

• across the galaxy towards their moon,

• dodging clunky meteorites

• and loopy space buggies.

• After a few close calls with a wandering satellite,

• Mark arrives first in two hours,

• and Bleebop gets there one hour later.

• Looks like Mark has the faster rocket,

• but let's check out the results with our DIRT equation.

• Begin by setting up a chart.

• Make four columns and three rows.

• Use DIRT to remember what to fill in.

• Each rocket will have information

• for distance, rate, and time.

• Mark's rocket went 150 miles,

• we don't know the rate,

• and he got there in 2 hours.

• Bleebop's rocket went 240 miles,

• we don't know the rate,

• and the time is 1 hour after Mark,

• or 3 hours.

• Because we don't know Mark or Bleebop's rate,

• that number is going to be a variable

• in each equation,

• which we'll represent with x.

• We'll solve the equation

• for the variable to find its value.

• Mark finished first,

• Remembering DIRT, write down D=RT.

• 150 miles equals x times 2 hours.

• Divide both sides by 2 hours.

• This will leave x isolated

• on the right side of the equation.

• 150 miles divided by 2 hours

• is 75 miles over 1 hour.

• Mark's rate is 75 miles per hour.

• That's what mph means.

• It's the amount of miles over one hour.

• Still think Mark is faster?

• Let's set up the same equation for Bleebop and see.

• D=RT

• 240 miles equals x times 3 hours.

• Divide both sides by 3 hours.

• This will leave x isolated

• on the right side of the equation.

• 240 miles divided by 3 hours

• is 80 miles over 1 hour.

• Bleebop's rate is 80 miles per hour.

• Wow, even though Bleebop got there one hour later,

• it turns out he had the faster rocket.

• Mark seems pretty upset,

• but with aliens, you can never really tell.

• Thanks to DIRT, you now know how to calculate

• distance,

• rate,

• and time.

• In what other situations

• can you use the distance formula?

• You don't even need to be watching a space race.

• As long as you know two pieces of information

• for the formula D=RT,

• you can calculate any moving vehicle or object.

• Now, the next time you're in a car,

• you can let your friends know

• exactly when you'll be arriving,

• how fast you're going,

• or the distance you'll travel.

• It's as simple as DIRT.

Do you have a friend or a sibling

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B1 US TED-Ed equation rocket distance hour calculate

【TED-Ed】A trip through space to calculate distance - Heather Tunnell

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Kevin Tan posted on 2014/08/19
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