Saturday

April 19, 2014

April 19, 2014

Posted by **PDF** on Friday, February 3, 2012 at 8:12pm.

- Math -
**bobpursley**, Friday, February 3, 2012 at 8:24pmavgspeed=distance/time=50km/time=24km/hr

time=50/24 hrs

time rough+timesmooth= 50/24

sum of distances equals 50km or

30*timerough+12*(50/24-timerough)=50

timerough(30 -12)=50(1-1/2)

time rough= 25/18 hrs

distance rough= 25/18 * 12=50/3 km

check all that.

- Math -
**Reiny**, Friday, February 3, 2012 at 9:07pmLet the distance on good road be x km

then distance on rough road is 50-x km

time on good road = x/30

time on rough road = (50-x)/12

total time = x/30 + (50-x)/12

= (2x + 250 - 5x)/60

= (250 - 3x)/60

but total time = 50/24

so (250-3x)/60 = 50/24

3000 = 6000 - 72x

72x = 3000

x = 3000/72 = 125/3 or 41 .67 km

so 42.67 km were good road and

50 - 41.7 or 8.3 km were under repair.

check: total time = 50/24 = 2.083 hrs

time on good road = 41.67/30 = 1.389

time on rought road = 8.3/12 = .692

total time = 2.081 , close enough allowing for round-off

all checks out

**Related Questions**

Algebra - How do you work this out? Going downstream a tugboat averages 17 kph. ...

Physics - A motorist traveling at 30 m/s passes a parked police car. At the ...

Math - what value of m will make 4x-7y=5 and 9x+my=3 parallel? a car leaves town...

Math - a bus travels 240 kilometers at 60 kph and then returns at 40 kph.. what ...

math - The basement of a new home will have the following dimensions 30 feet ...

Math - A motorist traveling 55 mph is being pursued by a highway patrol car ...

Physics - A motorist drives along a straight road at a constant speed of 16.5 m/...

math - A ship sail S 40 degrees W for 4 hours at 30 kph. make a scale drawing

Physics - A motorist travels 1600 m at 80 m/s and 750 m at 100 m/s. What is the ...

Physics - A police radar has an effective range of 1.0 km, and a motorist's ...