20 miles in 15 minutes (one-quarter of an hour) 80 miles in 60 minutes (one hour) The car's average speed over the first quarter-hour is 80MPH. (No calculator. No head scratching. Just grade school mathematics.)
I think that this is one type of problem (per quantaties and units conversion) that kids should be learning about in school. It's actually a useful real life tool.
looks like rate or ratio puzzle if plug the distance 20 miles in the nominator and the time 15 min converted to seconds (15 x 60 = 900 seconds) in the denominator and divide both by 900, we'll yield the unit rate of the speed (20 : 900) / (900 : 900) = (1 / 45) / (1) = 1/45 miles per second 1 mile = 1609.344 meter --> 1/45 x 1609.344 meter = 35.7632 per second ============================================================== 20 miles / 15 minutes = y / 60 minutes 20 x 60 = y x 15 1200 = 15y 1200/15 = 15y/15 80 = y ---> 80 mph
@@cuzz63 I think some Texas highways have an 85mph limit...the question then is why bother with a limit...this is what had been done on some remote roads in Australia...no one around to help in a crash.
34 posts here just have 80 without any description of how they found it, and this after John's repeated urging to show your work. All posts here are either 2 or 3 weeks ago, but for this, my post.
This simple problem gives an opportunity to learn how to do conversions of units. It is amazing how a Math problem could be solved in different ways! The most important point is that we should truly understand the reasoning properly. Our great teacher, Mr John is explaining how to think and understand and solve this problem, in different ways! Thank you, Mr John 🙏🏽
To do this rate over time/speed 60 miles = 1hour 20 miles= 60/20=30 30 miles =1/2 hour 60 miles=1hour 20 miles= 60/30= 20 minutes 15 miles=20 min 60miles/15 milesx20 miles 4milesx20 miles = 80 miles So the car is traveling 80 miles /hr
The speed is zero, because motion is impossible . An object must occupy a definite location at any instant of time . Since there is no space of time in an instant there is no time for motion. Hence motion is just imagination.
If you actually have to drive 80 miles an hour in a 55 mile per hour zone, if you get a speeding ticket you might have to go to driving school and pay a big ticket cost, or worse.
Speed = miles per hour so Speed = 20 . 4 miles / 15 . 4 minutes = 80 miles per hour Also: 20 miles in 15 minutes is 40 miles in 30 minutes is 80 miles in 60 minutes is 80 miles per hour
Stupid question, and stupid answer. A child in grade 3, knows that if you are travelling at a speed of 80 miles per hour, you will cover 20 miles in a quart of an hour.
Question needs more information. Speed in what units? The actual average speed is 20 miles per quarter hour. The question doesn't ask for mph. Still, it gets clicks and comments. Good for monetization.
Anyone who thinks it's easy because 15 minutes is a nice and simple quarter of an hour... Okay. Now do it for a car travelling 21 miles in 12.5 minutes.
By dividing 21 miles with 12.5 we can find how many mile we going in 1 minute and thats 1.68 mile per minute.and now if we wanna find how many mile we'll go with this in one hour we can just multiply it by 60=1 hour. 1.68*60= 100.8mph is it correct?
This might be a problem for every student in the Baltimore Public Schools. One year *EVERY* student, in every school, failed the State Math Exam. 0 passed!
The number of miles a car goes in 15 minutes = 20 Calculating the number of miles the car goes in 60 minutes or in 1 hour: 20 miles 60 min. ----- x ---- 15 min. 1 hour 20 miles 4 ----- x ---- 1 1 hour (Minutes on the numerator and denominator got canceled off.) 80 miles/hour The speed of the car is 80 mph.
@@geniferteal4178 The first fraction is miles per minute. To convert that to mph we need to multiply it by 60. Though it's often left as implicit rather than, as here, explicit, a whole number being multiplied by a fraction is technically treated as being itself over 1 so that the denominators can be multiplied. The steps not shown above are: 20/15 × 60/1 = 1200/15 Then we simplify: 1200/15 = 80/1 = 80 mph
@@geniferteal4178 That is because 60 minutes equals one hour. In order to convert minutes into hours, the equation can be set up in that way. Then, the minutes in the denominator and the minutes in the numerator get canceled with each other. Miles on the numerator and hours in the denominator are left behind. 60 minutes divided by 15 minutes will leave just 4, while minutes get canceled off. 20 miles times that 4 gives 80 miles. Then, the units that are left at the end are miles per hour. 80 miles per hour. (80 mph).
Taking 13 minutes to explain this is in my opinion poor teaching. A good teacher would simplify the problem. I enjoy the maths challenges, however I find the explanations highly irritating. The answer is an AVERAGE of 80 mph!!
The answer is $350, the amount of the speed ticket for doing 80 mph. 😆
Depending in which state or territory in Australia but can range from "on the limit" in the NT, to "crush the car" in Victoria
In Utah we can go 80 in the boondocks on the interstates, but slower in populated areas.
Solved it in my head in five seconds.
Me too- old school
What took you so long?
I agree with the below comment. 20 miles is quarter hour. Mult. by 4 for the full hr... Yields 80...
80mph. (15 mins is 1/4 hour)
Then multiply 20 by 4 to get your 80mph.
By far the quickest route to the answer. It was another "at a glance" solution.
The car's AVERAGE SPEED over the first quarter-hour was 80MPH. It MAY continue at that same speed for the next 45 minutes. Or, not!
Wrong. The RATE is 80 MPH. The question was not how far the car goes in an hour.
20 miles in 15 minutes (one-quarter of an hour)
80 miles in 60 minutes (one hour)
The car's average speed over the first quarter-hour is 80MPH.
(No calculator. No head scratching. Just grade school mathematics.)
.... but, since you suggest it's so easy, did you really need to explain 🤦🏼
80 mph
Nice answer; however, the challenge is to show one's work
Factorise to 4:
15 mins x 4 = 60 mins (1 hour)
20 miles x 4 = 80 mph
I think that this is one type of problem (per quantaties and units conversion) that kids should be learning about in school. It's actually a useful real life tool.
looks like rate or ratio puzzle
if plug the distance 20 miles in the nominator and
the time 15 min converted to seconds (15 x 60 = 900 seconds) in the denominator
and divide both by 900, we'll yield the unit rate of the speed
(20 : 900) / (900 : 900) = (1 / 45) / (1) = 1/45 miles per second
1 mile = 1609.344 meter --> 1/45 x 1609.344 meter = 35.7632 per second
==============================================================
20 miles / 15 minutes = y / 60 minutes
20 x 60 = y x 15
1200 = 15y
1200/15 = 15y/15
80 = y ---> 80 mph
ok on the Autobahn and Northern Territory roads in Australia..... 80mph =128km/h...it's pretty fast. Cheers from Australia
Thats the speed limit on our interstate.
@@cuzz63 I think some Texas highways have an 85mph limit...the question then is why bother with a limit...this is what had been done on some remote roads in Australia...no one around to help in a crash.
Super easy. Use the factor-label method for all types of unit conversions.
I did that in the time it took to read it. 80 mph.
80
The speed of the car is 20miles/15min., or 288,000feet/sec, or 80miles/hour., or ...
Rate problems extend to calculus and physics. R×T=D
Thank you
34 posts here just have 80 without any description of how they found it, and this after John's repeated urging to show your work. All posts here are either 2 or 3 weeks ago, but for this, my post.
This simple problem gives an opportunity to learn how to do conversions of units.
It is amazing how a Math problem could be solved in different ways!
The most important point is that we should truly understand the reasoning properly.
Our great teacher, Mr John is explaining how to think and understand and solve this problem, in different ways!
Thank you, Mr John 🙏🏽
Easy, the car goes at a speed of 20 miles per 15 minutes. (You never specified the required units.)
Oh, yeah. 😉
To do this rate over time/speed
60 miles = 1hour
20 miles=
60/20=30
30 miles =1/2 hour
60 miles=1hour
20 miles=
60/30= 20 minutes
15 miles=20 min
60miles/15 milesx20 miles
4milesx20 miles = 80 miles
So the car is traveling 80 miles /hr
80 miles in 15 min I meant
Ans=20×4=80 Ans =80 KM / Hr. (15×4)=60 m. or 2 hr.
The speed is zero, because motion is impossible . An object must occupy a definite location at any instant of time . Since there is no space of time in an instant there is no time for motion. Hence motion is just imagination.
😂😂😂
80 mph. 20 in 15 min = 80 in 60 min or 1-hr thus 80 mph
If you actually have to drive 80 miles an hour in a 55 mile per hour zone, if you get a speeding ticket you might have to go to driving school and pay a big ticket cost, or worse.
Assume we're on the autobahn.
How on earth can it take more than 13 minutes to solve this "problem?" 13 seconds maybe.
Speed = miles per hour so Speed = 20 . 4 miles / 15 . 4 minutes = 80 miles per hour
Also: 20 miles in 15 minutes is 40 miles in 30 minutes is 80 miles in 60 minutes is 80 miles per hour
What a load of dribble, find the fraction of the whole and multiply,
11/3
I was taught this as a triangke using S for speed nit R so
S
T D so T=S/D D=S/T
S=T×D
Stupid question, and stupid answer. A child in grade 3, knows that if you are travelling at a speed of 80 miles per hour, you will cover 20 miles in a quart of an hour.
And when you're introducing people to a subject, you use simple examples to illustrate your explanation.
Adding more units made it more easier for me to understand and to recheck my thinking. Please reconsider adding them more.
Question needs more information.
Speed in what units? The actual average speed is 20 miles per quarter hour. The question doesn't ask for mph.
Still, it gets clicks and comments. Good for monetization.
Never heard such a load of rubbish. Solved in 5 seconds, 15 mins x 4 20 x 4 = 80mph. What is wrong with this guy?
m/45sec..., i just recalled the formula learned in middle school, don't know whether it's correct or not...
13 mins for this? It takes 2 seconds to work it out.
20 mph because he live in Wales. Obey the Welsh Assembly
117.333~ Feet per second 😂... or if you're lazy 80 mph or 128.747 kmph
20 in 15 is 40 in 30 mins, 60 min is 1 hr .Therefore 2 times 40 is 80 mph
x=(20 mi/15 min)(60 min/1 hr)
x=80 mi/hr
The car is going 80 mph
Way too complicated...
(20 miles) / (1/4 hour) = 80 mph
4 x 15 = 60: 20 x 4 = 80 very simple
Do you REALLY need to explain "speed"???🤦🏼
This is the MOST FEEBLE question ever 😡
Anyone who thinks it's easy because 15 minutes is a nice and simple quarter of an hour... Okay. Now do it for a car travelling 21 miles in 12.5 minutes.
100.8 mph
By dividing 21 miles with 12.5 we can find how many mile we going in 1 minute and thats 1.68 mile per minute.and now if we wanna find how many mile we'll go with this in one hour we can just multiply it by 60=1 hour. 1.68*60= 100.8mph
is it correct?
21 miles in 12.5/60 of one hour
100.8MPH average for the first 0.20833... hours
Yep you're all correct.
21/12.5 × 60 = 100.8
And if you're not on the autobahn or similar, you're in deep trouble.
Why?
What is the car's speed? Good question. It is moving?
got 80 mph simple multiply by 4 thanks for the fun
80 mph and tickets $450
20/0.25=80
Maybe an opportunity lost here to talk about dimensional analysis?
Should be an average of 80 mph as the car could be changing its speed sometimes
20/15*60=80
John would take points off for not showing any units.
miles/minutes × minutes/hour= mph
. Minutes cancel out
79.999 mph
X = 80 mph
I did 20×60= 1200÷15=80 is that good enough?
Is this really a problem.
This might be a problem for every student in the Baltimore Public Schools. One year *EVERY* student, in every school, failed the State Math Exam. 0 passed!
80 miles an hour
80 mph.
4\3 miles per hour
80mph
80 milles in 15 min i meant
So simple .just multiply by 4
80 miles per hr.
did you start from 0 miles per hour
80....this is easy
I just divided 20 by 1/4.
In other words you multiplied by 4
Easy but over the speed limit
But your honor, there was no posted speed limit! How were we to know?
13 minutes to do the division: 20 / ¼ = 80 really ???
So much for passing the SAT.
100mi./hr jan
The number of miles a car goes in
15 minutes = 20
Calculating the number of miles the car goes in 60 minutes or in 1 hour:
20 miles 60 min.
----- x ----
15 min. 1 hour
20 miles 4
----- x ----
1 1 hour
(Minutes on the numerator and denominator got canceled off.)
80 miles/hour
The speed of the car is 80 mph.
Does anybody understand this way of calculating it?
@@geniferteal4178
It is converting the speed, 20 miles in 15 minutes
to (number of) miles per hour.
@@chrisdissanayake6979 i don't understand why you have sixty minutes over one hour
@@geniferteal4178 The first fraction is miles per minute. To convert that to mph we need to multiply it by 60. Though it's often left as implicit rather than, as here, explicit, a whole number being multiplied by a fraction is technically treated as being itself over 1 so that the denominators can be multiplied. The steps not shown above are:
20/15 × 60/1 = 1200/15
Then we simplify:
1200/15 = 80/1 = 80 mph
@@geniferteal4178
That is because 60 minutes equals one hour.
In order to convert minutes into hours, the equation can be set up in that way.
Then, the minutes in the denominator and the minutes in the numerator get canceled with each other.
Miles on the numerator and hours in the denominator are left behind.
60 minutes divided by 15 minutes will leave just 4, while minutes get canceled off.
20 miles times that 4 gives 80 miles.
Then, the units that are left at the end are miles per hour.
80 miles per hour. (80 mph).
This is a little too easy
20/15 = 4/3 mpm
4/3 × 60 = 240/3 = 80 mph
Taking 13 minutes to explain this is in my opinion poor teaching. A good teacher would simplify the problem. I enjoy the maths challenges, however I find the explanations highly irritating. The answer is an AVERAGE of 80 mph!!
I got the same answer with proportions. 20 x 60 divided by 15 = 80.
🤷🏼♂️🤦🏼
1 1/3 mile/minute = 80 mile / hr
1.33 miles/ minutes
Sorry, I don't know what miles are. I only know km, miles should be scrapped !!!
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