algebra

[pboland]

A female shark swam from South AFrica to Australia adn back in record time, about nine months. The round trip distance is 12,400 miles. Assume that the shark maintained a constant speed, and never slept. Find her speed in miles per hour.
I am having trouble figuring out the formula to use, I know that d=rt, where di=distance, r=rate of speeed and t=time. t=d/r. Would r=d/t?

 

[TchrQbic]

A female shark swam from South AFrica to Australia adn back in record time, about nine months. The round trip distance is 12,400 miles. Assume that the shark maintained a constant speed, and never slept. Find her speed in miles per hour.
I am having trouble figuring out the formula to use, I know that d=rt, where di=distance, r=rate of speeed and t=time. t=d/r. Would r=d/t?

Certainly. That's why when you're driving your speed is miles per hour, often written miles/hour (d/t).

 

[pboland]

Would this then be correct:
r=d/t
r=12,400/9
r=1377.778 or 1378 miles per hour?

 

[TchrQbic]

Would this then be correct:
r=d/t
r=12,400/9
r=1377.778 or 1378 miles per hour?

Pay attention to the units. The 9 in the problem was months. To change 12,400 miles/1 month to miles per hour, you need to multiply 12,400/9 times
1 month/30 days * 1 day/24 hours. That will cancel all units (month, day) but hours, and the final result will be 12,400/30*24 miles/ hour. You can do the figuring.

 

[soroban]

Hello, pboland!

Would this then be correct?

\(\displaystyle r\,=\,\frac{d}{t}\;\;\) . . . correct!

\(\displaystyle r\,=\,\frac{12,400}{9}\;\;\) . . . right!

\(\displaystyle r\,=\,1377.778\) or \(\displaystyle 1378\)mph . . . . heh!

That is a very fast shark, isn't it?

You had: \(\displaystyle \,\frac{12,400\text{ miles}}{9\text{ months}}\;=\;1378\) miles per month.

Convert: \(\displaystyle \,\frac{1378\text{ miles}}{1\text{ \sout{month}}}\,\times\,\frac{1\text{ \sout{month}}}{30 \text{ \sout{days}}}\,\times\,\frac{1\text{ \sout{day}}}{24\text{ hours}} \:= \:\frac{1378\text{ miles}}{720\text{ hours}}\;\approx\;1.9\) mph