Three word problems I don't understand. Please help soon.

[lauren_z8]

Michael drove to a friend's house at a rate of 40 mi/h. He reaturned by the same route at a rate of 45 mi/h. The driving for the round trip was 4 h. What is the distance michael traveled?

[quote:34jff6pt]In the 2000 Olympics, Jones won the gold medal in the 100-meter race with a time ofd 10.75 sec. In the 1868 Olympics, Tyus won the gold in the 100-meter race in 11.08 sec. If they ran in the same race repeating their respective times, by how many meters would jones beat Tyus?

[quote:34jff6pt]Suppose you have $5000 to invest. A certificate of deposit (CD)earns 6% annual interest, while bonds, which are more risky, earn 8%annual interest. You decide to invest $2000 in a CD and the rest in bonds. How much interest will you have earned at the end of one year? Of two years?

I am in algebra 2 honors, and story prblems confuse me so much. So dumb it down. Thank you for your help, or thanks for looking anyway[quote:34jff6pt]

[/quote:34jff6pt][/quote:34jff6pt][/quote:34jff6pt]

 

[kaebun]

for the third one i think you set it up like this...
(.06)2000+(.08)(5000-3000)=x
and thats how much in trest for 1 year does that make sense?

 

[Guest]

average speed =distance/time
speed#1 = 100/10.75

speed#2 = 100/11.08

take speed#2 and multiply it by (11.08-10.75) and you will have the distance

 

[lauren_z8]

thank you guys. these things are so hard. but yeah i get it, i hope.

 

[Linty Fresh]

OK, I think I'm doing this right, but my numbers are a little wonky. They're not even.

OK, so given a return trip over an equal distance at different rates taking four hours, we have:

Time(Mike->Friend)=t (in hours)
Time(Friend->Mike)=4-t

Rate(Mike->Friend)=40 mph
Rate(Friend->Mike)=45 mph

Therefore, since Distance = Rate*Time (because Rate=Distance/Time):
Distance (Mike->Friend)=40t
Distance (Friend->Mike)=45(4-5) or 180-45t

Now the two distances should be equal, so:

40t=180-45t

85t=180
t=180/85 or 2.1176

Sooooooo . . .

Add up the whole thing like so:
40(2.11176) + 180-45(2.1176)=169.45 miles total, give or take a tenth.

Could someone check my math on this? I think it's kosher, but then again, I'm new to this.

 

[Linty Fresh]

thank you guys. these things are so hard. but yeah i get it, i hope.

You know what really helped me with these sorts of problems? There's a book out there called How to Solve Word Problems in Algebra by Mildred Johnson and Tim Johnson. It shows you how to solve problems like the ones you posted here. I got mine at the local Borders bookstore, and it was a lifesaver in getting me to the next level. I'd totally recommend it.

Now if only there was a book devoted to logarithms and exponential functions :?

 

[Denis]

Add up the whole thing like so:
40(2.11176) + 180-45(2.1176)=169.45 miles total, give or take a tenth.
Could someone check my math on this? I think it's kosher, but then
again, I'm new to this.

Correct; well done, LF!