David's horse

Algebra Level 2

David loves to ride his horse. When he is riding his horse, he travels at a rate of 10 10 mi/hr, and when he is walking, he travels at a rate of just 3 3 mi/hr. David goes on a 4 4 -hour trip, traveling for a while on his horse and walking the rest of the way, and travels 29.5 29.5 miles. For how many minutes was David riding his horse?


The answer is 150.

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19 solutions

Consider the formula d i s t a n c e = r a t e × t i m e distance = rate \times time

Let x x be the amount of time taken riding and 4 x 4 - x walking.

10 x + 3 ( 4 x ) = 29.5 10x + 3(4 - x) = 29.5

x = 2.5 h o u r s x= 2.5 hours which is equal to 150 m i n u t e s . 150 minutes.

aeosome......................

ashik sunny - 7 years, 5 months ago

great

Kishore Kumar - 7 years, 5 months ago

excellent

sunil kumar - 7 years, 5 months ago

very good

Akshay Gupta - 7 years, 5 months ago

Nice

Angelo William Parco - 7 years, 5 months ago

ah,,yeah physics ugh!!!

Kim Echizen - 7 years, 5 months ago

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Physics? I thought this was basic algebra!

Kevin Mo - 7 years, 5 months ago

Great

Delowar Sami - 7 years, 4 months ago

great presenc of mind

Vijay Patil - 7 years, 4 months ago
Alexander Sludds
Dec 21, 2013

Setting up the equation we find that 10 t h + 3 t w = 29.5 10*t_{h}+3*t_{w}=29.5 and t w + t h = 4 t_{w}+t_{h}=4 . Solving we find that 7 t h = 17.5 7*t_{h}=17.5 . Solving for t h t_{h} and multiplying by 60 60 we find that the answer is 150 150 .

Ajay Maity
Dec 23, 2013

Let's say David was riding his horse for x x hours.

Then, he was walking for 4 x 4 - x hours, as the total trip was of 4 4 hours.

Since the total distance travelled is 29.5 = 59 2 29.5 = \frac{59}{2} miles, we have

10. x + 3. ( 4 x ) = 59 2 10 . x + 3 . (4 - x) = \frac{59}{2}

10 x + 12 3 x = 59 2 10x + 12 - 3x = \frac{59}{2}

7 x + 12 = 59 2 7x + 12 = \frac{59}{2}

7 x = 59 2 12 7x = \frac{59}{2} - 12

7 x = 35 2 7x = \frac{35}{2}

x = 35 2 × 7 x = \frac{35}{2 \times 7}

x = 5 2 x = \frac{5}{2} hours

In minutes, it will be

x = 5 2 × 60 x = \frac{5}{2} \times 60 minutes

x = 150 x = 150 minutes

That's the answer!

nice

Abul Hossain - 7 years, 5 months ago

good

zahra rasul - 7 years, 5 months ago

nice

Vijay Patil - 7 years, 4 months ago
Siddharth Yadav
Dec 23, 2013

THIS IS QUITE SIMPLE!

The total distance travelled is 29.5 miles. We know that when David is riding he is at 10 miles/hour and when he is walking he is at 3 miles/hour.

Let 'R' be riding time taken, 'W' be walking time taken and 'T' be the total time taken; hence we can write;

T= R + W

which is; 29.5T= 10R + 3W ( since riding speed is 10mph and walking speed is 3mph)------> eq. 1

We also know that the total amount of time taken is 4 hours; hence;

4=R + W ------> eq.2

From eq.2 we get; W= 4 - R------->eq.3

Putting eq.3 in eq.1; We get; 29.5T= 10R + 3(4-R)

29.5T= 10R + 12 - 3R

29.5T= 7R + 12

R=29.5T-12 / 7

R=2.5T

Therefore David rode for 2.5 hours = 150 minutes! ENJOY!

Budi Utomo
Dec 23, 2013

29.5 = 25 + 4.5 ---> 25/10 hour + 4.5 /3 hour = 4 hour ---> 2 .5 hour + 1. 5 hour = 4 hour. ---> [2 .5 hour] + 1. 5 hour = 4 hour. ----> So, David was riding 2.5 hour = 2 .5 x 60 minutes = 150 minutes. Answer : 150

Lorenc Bushi
Dec 23, 2013

Let x x be the distance he made by riding his horse.Let x 1 x_1 be the distance he made by walking.Let t t be the time he was riding his horse.Let t 1 t_1 be the time he was walking during the trip.We have :

10 = x t 10=\frac{x}{t} ( 1 ) (1)

3 = x 1 t 1 3=\frac{x_1}{t_1} ( 2 ) (2)

From the first equation we have :

10 t 1 10.5 = x 1 10t_1-10.5=x_1

3 t 1 = x 1 3t_1=x_1

Therefore we have 10 t 1 10.5 = 3 t 1 10t_1-10.5=3t_1 where we obtain t 1 = 1.5 t_1=1.5 hours and t = 2.5 t=2.5 hours which is equal to 150 150 minutes .So t = 150 \boxed{t=150 }

where 10.5 come from?

Star Buck - 7 years, 5 months ago

The answer is 150 and arrived by simple arithmetic.

Callum Farnden
Feb 14, 2014

David travels for 4 hours. In this time, he travels 29.5 miles.

D=st, you can do this for both horse and walking, finding the sum at the end- which is equal to the total distance (29.5mi).

Thus if h is time on horse,

29.5mi=10h + 3w, w=4-h 29.5mi=10h+3(4-h) 29.5=7h+12, h=17.5/7 h=2.5

The question asks you to convert this into minutes - 2.5 hours = 150 minutes.

The key leap here was realising that time walking can be written as (4-h). This means you have only one unknown in your equation for time on horse and thus that it can be solved to give 150 minutes.

Bharath Bhat
Feb 1, 2014

the only combination for 29.5 mil is 29.5 = 10+10+5+3+1.5 i.e he rode the horse for the first 2 and a half hrs and then walked for the rest. so he rode for 150 mins.

Muhammad Jahangir
Jan 24, 2014

time on horse= x, time on foot = y, x+y=4 or x= 4-y 10x+3y=29.5 substituting x. 40-10y+3y=29.5 or y = 1.5 and x=2.5 so 2.5*60=150min

Tushar Ahooja
Jan 23, 2014

Let the time travelled by David while riding be x hours and while walking be y hours.

       RIDING

SPEED=10 miles/hr
TIME =x hr
SINCE D=S*T,
D=10x


      WALKING

SPEED=3 miles/hr TIME =Y hr
SINCE D=S*T,
D=3y

ACCORDING TO QUESTION, 10x+3y =29.5 and x+ y =4

By solving, x=2.5 hr and y=1.5 hr

Therefore time spent by David riding horse=2.5 hr =(2.5 *60) min =150 minutes

x/3 + (29.5 - x)/(10) = 4

x/3 - x/10 = 1.05

7x/30 = 1.05

x = 4.5 miles

So therefore David spend (29.5 - 4.5)/10 * 60 = 150 minutes riding the horse.

Kamaljeet Singh
Jan 18, 2014

let x hour David ride and y hour David walk then 10x+3y=29.5..........(i) but y=4-x..........(ii) then x=2.5 in minutes x=2.5*60 x=150

Sandeep Sharma
Jan 16, 2014

David rides his horse 2.5 hrs and travels 25 miles.(2 hr=20 miles and for 30 min=5 miles) by walking for 1.5 hrs,he covers 4.5 miles(1 hr=3 miles and for 30 min=1.5 miles) so for total 4 hrs trip he travels 25+4.5=29.5 miles . hence David rides his horse for 2.5 hrs i.e.., 150 min

Agustia Larasari
Jan 10, 2014

x= time spent to travel with horse y = time spent when walking

29.5 = 10 x + 3 y x + y = 4

then,

y = 4 - x 29.5 = 10 x + 3 (4 - x) = 10 x + 3 4 - 3*x

17.5 = 7*x

x = 2.5 in minutes = 2.5*60 = 150 minutes

You can set up this equation:

10x + 3(4 - x) = 29.5

where x is the number of hours he rides the horse. The quantity (4 - x) represents the rest of the 4-hour trip, when he was walking. From this we obtain x=2.5, but since x is in hours, we must multiply by 60 to get the number of minutes he rode his horse.

The final answer is 150 minutes.

Kevin Uning
Jan 8, 2014

Here's the variable and what they represents in my explanation Time spent on: Walking = a Riding on horse = b

The time spent = 4 hours. 4 hours = a hours + b hours Because the total time spent on the journey is the total time spent riding on horse(b) and walking(a). But let's erase the 'hours' so... 4 = a + b

For the other equation: 29.5(miles) = 10b + 3a The total distance traveled by David is of course the sum of the distance of him walking and riding on horse. Why 10b? It comes from 10 mi/hour * b hour = 10b miles. So is 3a.

The rest left is combining the two equations by using either subtitution or elimination method. In the end, the result is 2.5 hours for b which is 150 minutes.

Yo,by rights,let x=riding on a horse,y=walking,total miles=29.5 miles, total hour=4 hours,

x + y = 4 10y + 3x = 29.5

by substituting,

y = 4 - x into 10x + 3y = 29.5 ,you will get x=2.5 hours(riding on horse),by multiply 60 to 2.5 hours you will get 150 mins,as 1hour=60 mins,thanks....

Prathyusha Konda
Dec 23, 2013

let x be the time(in hrs) spent for travelling by horse and y by walk. According to the problem, x + y = 4 and 10x+3y=29.5 . On solving these equations, x=2.5hrs i.e., 150 minutes

it can be done like.......1hr------------->10miles 4hr--------------->40 miles he has riden 29.5 miles for 4 hrs ;-in minutes (30 60)-(0.5 60)=150minutes

harsha gowda - 7 years, 5 months ago

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