A girl riding a motorcycle at 35 mph left home 2+(1/2) hours after her brother, who was riding a bicycle at 10 mph. How long will it take the girl on the motorcycle to overtake her brother if they are traveling in the same direction?

this is girl at home ----------------------------> her brother
35mph 2.5hrs 10mph 25miles has crossed!

okk
D=sxt
so, t=D/s t= .71hrs or 42min

Start a stop watch (that measures time in hours) at the moment that the brother left home.

How far is the brother from home when the stopwatch reads T hours? Come up with an equation for this so that when you plug in T the result is how far from home the brother is at that time.

Now do the same for the girl, keeping in mind that she doesn't leave home until T = 2.5 hours.

Get those two equations first.

The recognize that at whatever time, To, that they cross they are both the same distance from home.

 

A girl riding a motorcycle at 35 mph left home 2+(1/2) hours after her brother, who was riding a bicycle at 10 mph. How long will it take the girl on the motorcycle to overtake her brother if they are traveling in the same direction?

this is girl at home ----------------------------> her brother
35mph 2.5hrs 10mph 25+ (35-10)x.71 miles has crossed!

D=sxt
so, t=D/s t= 42.75/35 1.2hrs

Ask yourself some sanity check questions.

How far away from home is the brother when the girl starts out?

How far away from home is the brother one hour after the girl starts out? How far has the girl gotten in this amount of time?

How far away from home is the brother two hours after the girl starts out? How far has the girl gotten in this amount of time?

These are easy to solve and will let you place bounds on the answer so that you will know if your calculated answer has any chance of being correct.

 

A girl riding a motorcycle at 35 mph left home 2+(1/2) hours after her brother, who was riding a bicycle at 10 mph. How long will it take the girl on the motorcycle to overtake her brother if they are traveling in the same direction?

How far away from home is the brother when the girl starts out?

D=sxt 10x2.5=25miles away.

 

is this right?

 

A girl riding a motorcycle at 35 mph left home 2+(1/2) hours after her brother, who was riding a bicycle at 10 mph. How long will it take the girl on the motorcycle to overtake her brother if they are traveling in the same direction?


D=sxt 10x2.5=25miles away.

Okay. Now answer the next question.

 

is this right?

Yes. That you even had to ask this is not a promising sign, but we'll take what we can get and push on.

 

Remember to bear the suggestions in post #262 in mind

 

Why not have him draw a plot, before he derives an equation? Let him plot the brothers distance/time rate......and then her’s. It relates all the references.

A picture always helped me.

 

Why not have him draw a plot, before he derives an equation? Let him plot the brothers distance/time rate......and then her’s. It relates all the references.

A picture always helped me.

Indeed! An intuitive approach may be helpful

Additionally, I feel adoption of the 'simultaneous technique' would greatly ease matters... Further to that, if we encouraged solving via addition (as opposed to substitution), he'd be 'on course' for linear algebra!

 

@RRITESH KAKKAR

I must be on my way -- I'll look in tomorrow - Rest assured that I've many more exercises where that one came from! -- I appreciate your show of genuine effort!

Please heed the advice of others! - Some of them are instructors by profession and nearly all of them are better instructors than I!!!

Best regards
HP

 

Why not have him draw a plot, before he derives an equation? Let him plot the brothers distance/time rate......and then her’s. It relates all the references.

A picture always helped me.

We've tried. Many times. I don't think it's come to pass yet.

 

I lost my patience trying to follow him on another post. It was like am.......I thought I was moving, but didn't go anywhere.

 

hello,
Sorry i was gone in market.

 

It all seems to be summed up by the old proverb: You can lead a horse to water, but you cannot make him drink.

 

link

 

Yes, exactly!

 

A girl riding a motorcycle at 35 mph left home 2+(1/2) hours after her brother, who was riding a bicycle at 10 mph. How long will it take the girl on the motorcycle to overtake her brother if they are traveling in the same direction?
Ask yourself some sanity check questions.

How far away from home is the brother when the girl starts out?
D=sxt 10x2.5=25miles

How far away from home is the brother one hour after the girl starts out? How far has the girl gotten in this amount of time?
D=sxt 10x2.5=25miles + sxt 10x1 = 35miles in 3.5hrs
girl has travel
D = SxT =35x1= 35miles


How far away from home is the brother two hours after the girl starts out? How far has the girl gotten in this amount of time?
D=sxt 10x2.5=25miles + sxt 10x1 = 35miles in 3.5hrs + sxt 10x1 = 45miles in 4.5hrs

girl has travel
D = SxT =35x2= 70miles


These are easy to solve and will let you place bounds on the answer so that you will know if your calculated answer has any chance of being correct.

 

It all seems to be summed up by the old proverb: You can lead a horse to water, but you cannot make him drink.

I like my version better: You can lead a student to water, but it's still a felony to drown them.

 

A girl riding a motorcycle at 35 mph left home 2+(1/2) hours after her brother, who was riding a bicycle at 10 mph. How long will it take the girl on the motorcycle to overtake her brother if they are traveling in the same direction?
Ask yourself some sanity check questions.

How far away from home is the brother when the girl starts out?
D=sxt 10x2.5=25miles

How far away from home is the brother one hour after the girl starts out? How far has the girl gotten in this amount of time?
D=sxt 10x2.5=25miles + sxt 10x1 = 35miles in 3.5hrs
girl has travel
D = SxT =35x1= 35miles


How far away from home is the brother two hours after the girl starts out? How far has the girl gotten in this amount of time?
D=sxt 10x2.5=25miles + sxt 10x1 = 35miles in 3.5hrs + sxt 10x1 = 45miles in 4.5hrs

girl has travel
D = SxT =35x2= 70miles


These are easy to solve and will let you place bounds on the answer so that you will know if your calculated answer has any chance of being correct.

And so what have you learned about the answer to the problem from these simple checks?

 

first tell it that right?