Easy grade 9 math! Help!

Question

A skier takes 2 min and 24s to complete a run of 1.8km. Determine the average speed of the skier, in m's.

 

(We are currently learning about linear equations. If that helps at all!)

 

Please help!

Answer 1

Hi Megan;

First, we must understand that the unit of time is presented in minutes and seconds, whereas the speed must be presented in meters/second.

(2 min)(60 s/1 min)+(24 s)

The unit of minutes is being multiplied and divided in the numerator and denominator.  Therefore, these cancel...

(2 min)(60 s/1 min)+(24 s)

(2)(60 s)+(24 s)

Now that the units are aligned, we may calculate...

120 s + 24 s=144 s

Second, we must understand that the distance is presented in km, whereas the speed must be presented in meters/second...

(1.8 km)(1000 m/1 km)

(1.8)(1000 m)=1800 m

 

distance=(rate)(time)

(distance)/(time)=rate

(1800 m)/(144 s)=rate

The units are now in m/s.  Let's calculate...

12.5 m/s=rate

 

Answer 2

d = 1800 m

t = 2*60+24 = 144 sec

v = d/t = 1800/144 = 12.5 m/sec <==Answer