SOLUTION: hello, how are you? i need a help please : Driving at a speed of 40 km / h, you need half an hour to reach the home. With what speed do you have to drive to get home in 20 minutes

Question 1159341: hello, how are you? i need a help please :
Driving at a speed of 40 km / h, you need half an hour to reach the home. With what speed do you have to drive to get home in 20 minutes?
Found 5 solutions by MathLover1, MathTherapy, josgarithmetic, ikleyn, greenestamps:
Answer by MathLover1(20849)   (Show Source): You can put this solution on YOUR website!

since minutes is of an hour, means time is times less than hour, consequently speed will be times greater
so, speed will be
proof:
as you know

if time is
and ->
if time is ->
so,
since in both cases distance is same, we have

Answer by MathTherapy(10551)   (Show Source): You can put this solution on YOUR website!

hello, how are you? i need a help please :
Driving at a speed of 40 km / h, you need half an hour to reach the home. With what speed do you have to drive to get home in 20 minutes?

She's WRONG, WRONG, WRONG, as usual! Besides, she makes this SIMPLE problem so, so COMPLEX!!
At 40 km/h, and needing hour to get home, it goes without saying/is OBVIOUS that the distance to home is:
With distance home being 20 km, speed to get there in is:
That's how SIMPLE this TRAVEL problem is!
Answer by josgarithmetic(39616)   (Show Source): You can put this solution on YOUR website!

Answer by ikleyn(52775)   (Show Source): You can put this solution on YOUR website!
.

You do not need to know or to use algebra for it.

Arithmetic and common sense are just enough . . .

Arithmetic PLUS common sense.

A bit of Arithmetic and a bit of common sense.

Answer by greenestamps(13198)   (Show Source): You can put this solution on YOUR website!

Informally, using common sense -- as tutor @ikleyn says:

The distance is the same; the time is 2/3 as much (20 minutes instead of 30). That means the speed has to be 3/2 as much.

40kmh * 3/2 = 60kmh

ANSWER: 60 km/hr

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