Schools back in...

[Andy225]

Math homework... bleh

Can anyone help me out with a few problems??

A man traveled a distance of D feet in S seconds but arrived 2 minutes late. How fast should he have traveled in feet per sercond to have arrived on time?

the answer is D Ft/ S-120 Sec.

I can't figure out the work involved to get that answer...

[Steel_Avatar]

Speed is distance over time. Your desired speed has the man traveling D distance in some time, say T. However, the man was attacked by a crazy Irishman as he neared the destination. As a result, his actual time was S, which was 120 seconds off. If he had been on time, he would have taken S - 120 (which is T) seconds to get there.

So your speed would be D / (S - 120) ft /s.

PS: No one uses Imperial anymore. Go metric, silly Yank/Brit

[Andy225]

yeah... thanks... how about another?

How many positive integers less then 500 are there all of whose digits are odd?

[LunarSolaris]

249

God, I'd forgotten how they word those types of questions so that they are hard to wrap your brain around. I suppose it's designed to help you think "outside the box" eh?

[DemBonez]

yeah... thanks... how about another?

How many positive integers less then 500 are there all of whose digits are odd?

0, 1, 3, 5, 7, 9 are the only digits we can use. 0's are used up on 10, 30, 50, 70, 90, 100, 110, 130, 150, 170, 190, 300, 310, 330, 350, 370, 390.

The ones not bolded can have a 1, 3, 5, 7, or 9 as a ones digit. So we have (15 * 6) + 2 = 92 integers less than 500.

I am tired so you should check my math, not sure if I missed anything.

[rplusplus]

I forgot the fun of school time and all the Math Homework Threads!

The best part about math homework......

I
NEVER
EVER
EVER
HAVE
TO
DO
IT
AGAIN!



EVER!


R++

[Alviarin]

249

God, I'd forgotten how they word those types of questions so that they are hard to wrap your brain around. I suppose it's designed to help you think "outside the box" eh?

One of us has misread the question. 249 may be the number of odd numbers between 0 and 500, but he needs numbers that have all odd digits.

Fairly simple, I think. I'm pretty good at messing simple stuff up, though. 1,3,5,7,9--5. Every other set of 10s will be odd, plus the original 1,3,5,7,9. So for every 10 sets of 10, five will contain odds, and we'll add in 5 for the original 1,3,5,7,9.

Now the hundreds. For xx, odds are possible. 1xx, odds are possible. 2xx, no. 3xx, yes. 4xx, no.

So 3 sets of 100 we'll look at. 5*5*3+5= 80. Five for 5 odd numbers; 5 for 5 out of every ten sets of ten beginning with an odd number, 3 for 3 possible fields of 100's to work from, and 5 for the extra 1,3,5,7,9 that are only possible in the first set of 100. I don't see any mistakes, but that doesn't mean they aren't there.


Don't be surprised if this is the overcomplicated way of doing it. It probably is.

edit: ah, but someone posted an answer before me. Dembonez, isn't 0 even?

[LunarSolaris]

Yeah, but the beauty of me missing the question is that I'm with R++.... I never ever have to do math homework again in my life! :teeth:

[London]

Wow, this makes me glad that I'm out of high school. I sucked at math.

[rplusplus]

Wow, this makes me glad that I'm out of high school. I sucked at math.

You never truly escape Math... But you don't need to use complex formulae to balance the old checkbook. And most things these days are full of computers you don't even need most math skills. My bimmer tells me how full the gas tank is and computes the gas milage and will tell me how far I can drive on the gas left in the tank.

Computers are making it so people rely less and less on the basics.

R++