Thread: help!

"1. A train travels 35 miles per hour for 170 minutes
How far will the train travel in this time?

A car completed this same journey in 60% of the time the train took
Find the average speed of the car in mph

2. Y is inversely proportional to X². When Y=4, X=3.
Find an equation linking X and Y.

If X = 6 find the value of Y. (Hint, use the equation you've found above)"

there's no words to explain how confused i am right now

Originally Posted by amy15

2. Y is inversely proportional to X². When Y=4, X=3.
Find an equation linking X and Y.

If X = 6 find the value of Y. (Hint, use the equation you've found above)"

there's no words to explain how confused i am right now

"Y is inversely proportional to X²"
$\displaystyle -\,\, Y = \frac{k}{X^2}$

"When Y=4, X=3"
$\displaystyle -\,\, 4 = \frac{k}{3^2} \Rightarrow k = 36$

"Find an equation linking X and Y."
$\displaystyle -\,\, Y = \frac{36}{X^2}$

"If X = 6 find the value of Y. (Hint, use the equation you've found above)"
$\displaystyle -\,\, Y = \frac{36}{6^2}\Rightarrow Y = 1$

"there's no words to explain how confused i am right now "
$\displaystyle -\,\,\text{Oops....At least, I hope you are not now}$

thanks! i'm not so confused anymore

1: $\displaystyle \text{distance}=\text{speed}\times\text{time}$

In this case, the speed is 35 mph, and the time is 170 minutes ($\displaystyle {170}\div{60}$ hours)

so the distance that the train travels is $\displaystyle 35\times (170\div60)= 99.167$ miles.

The car traveled 99.167 miles in 60% of 170 minutes.
So it travelled 99.167 miles in $\displaystyle \frac{170}{100}\times60=102$ minutes ($\displaystyle 102\div60=1.7$ hours)

$\displaystyle \text{speed}=\frac{\text{distance}}{\text{time}}$

Therefore the average speed is $\displaystyle \frac{99.167}{1.7}=58.334$ mph