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## #1 Re: Help Me ! » Helicopter problem » Yesterday 10:28:59

bob bundy wrote:

hi Mathegocart

Work back from the available fuel.  6600 to start but 1200 must be kept as reserve and half hour = 600 for the transfer so the helicopter has 6600 - 1200 - 600 = 4800 for its journey.  It must go out and back so it can travel to a point at sea 2400 pounds of fuel away from the hospital = 2 hours of flight time.

In 2 hours the ship will cover 20 miles and the helicopter 300 miles so they won't meet.  That's why the helicopter must wait while the ship gets nearer before taking off.

So wait while the ship travels 80 miles, then set off and meet at a point 300 miles from the hospital.

I'm assuming the two must be stationary during the transfer.  You could shave a bit more off the time if the helicopter can meet the ship, turn around and match its speed while both travel towards the land.  Then once the passenger is aboard the helicopter, it is nearer the hospital so won't take 2 hours to get there.  Can you re-calculate using this interpretation? post back if you want me to try it.

Bob

leave the ship to get to the ship as quickly as possible? We do not go back to the ship and then back to the hospital. We just want to know the time to go to the ship.

## #2 Re: Help Me ! » Helicopter problem » Yesterday 10:06:08

bob bundy wrote:

hi Mathegocart

Work back from the available fuel.  6600 to start but 1200 must be kept as reserve and half hour = 600 for the transfer so the helicopter has 6600 - 1200 - 600 = 4800 for its journey.  It must go out and back so it can travel to a point at sea 2400 pounds of fuel away from the hospital = 2 hours of flight time.

In 2 hours the ship will cover 20 miles and the helicopter 300 miles so they won't meet.  That's why the helicopter must wait while the ship gets nearer before taking off.

So wait while the ship travels 80 miles, then set off and meet at a point 300 miles from the hospital.

I'm assuming the two must be stationary during the transfer.  You could shave a bit more off the time if the helicopter can meet the ship, turn around and match its speed while both travel towards the land.  Then once the passenger is aboard the helicopter, it is nearer the hospital so won't take 2 hours to get there.  Can you re-calculate using this interpretation? post back if you want me to try it.

Bob

Thank you, bundy, but I do not clearly get the answer. Would it be 1:30 PM?

## #3 Help Me ! » Square coordinate problem » Yesterday 09:32:10

Mathegocart
Replies: 2

1. One diagonal of a square lies on the y axis of a coordinate system. The coordinates of 1 corner is 3,7. What are the coords of the opposite corner?

## #4 Help Me ! » Confirmation of problem » Yesterday 08:00:26

Mathegocart
Replies: 1

A painter has 4 colors and a box. He wishes to paint the inside in 1 color and the outside in another color. How many ways are there to color it?
Is it 12?

## #5 Re: Help Me ! » angles » Yesterday 04:59:06

I am going to interpret that you are saying "why do we use radians instead of angles in trigonometry?"
Welll many trig functions have many characteristics(periods,allowed values, etc) that make radians particularily handy.
Look, which looks more convenient? Radians....or degrees?

The number pi, as strange as it seems, is at the heart of mathematics. The number 360 isn't. Clinging to 360 instead of pi will not allow you to see the beauty of trigonometry.
Let's just start with any old circle and wrap the radius of the circle around the circle.

See how it forms a angle? We'll call that a RADIAN.
Now, let’s take that radius and wrap it around the outside of the circle. See how it forms an angle? We’ll call that angle 1 radian.

Now we have fit nearly 6 radians in

There's a little bit remaining.
We get
C = 2πr.
There are exactly 2pir radians in a circle!

## #6 Help Me ! » Helicopter problem » 2016-07-25 09:28:49

Mathegocart
Replies: 6

You are a pilot of a medical evacuation helicopter. At 5:30 am, you receive word that a passenger  on a ship fell ill and needs to be airlifted as quickly as possible to the nearest hospital, which is where you and the helicopter are located. The cruise ship is 400 miles away from you, where the nearest hospital is found. The ship is making it's way at 10 mph to your port. Your helicopter only has 6600 pounds of fuel, and it burns 1,200 pounds of fuel every hour when it is airborne. Airlifting a passenger takes 30 minutes. Federal law mandates that pilots most retain an hours worth of fuel at all times. If your helicopter travels at 150 miles per hour, at what time must you leave the ship to get to the ship as quickly as possible?
This was one of my practice HW problems and the answer is apparently not 5:30.AM
Could someone give me a detailed explanation on why this isn't 5:30 AM and what the answer is?
THOUGHT PROCESS;
The helicopter can obviously not travel for more than 5 hours since it must maintain an hours worth of fuel.
Now the heli and boat have a 400 mile distance between eachother.
x = time since 5:30 AM
y = time after 5:30 AM when starting the helicopter
now the helicopter's traveled distance is 150(x-y), and the boat's distance is 10x. Summing these expressions, we get 160x-150y = 400, which is (16/15)x- 40/15.
Getting to the ship as quick as possible is minimizing both x and y, and I got 2.5,0.
So is it 8:00 AM?

## #7 Re: Exercises » Exponent Slash, #1 » 2016-07-21 02:12:24

6 also is a solution, and 6 is not a cube. $\frac{6!}{6^{2}}$ = 20

## #8 Re: Exercises » Exponent Slash, #1 » 2016-07-21 02:10:10

bobbym wrote:

Hi;

Both answers are reasonable solutions, also thickhead has a good soultion as well.

## #9 Re: Exercises » Exponent Slash, #1 » 2016-07-21 02:07:08

Thickhead, could you explain the process on the inequality? I used a bit of Cauchy Schwarz on this.

bobbym wrote:

Hi;

Correct.

## #11 Exercises » Exponent Slash, #1 » 2016-07-19 07:20:45

Mathegocart
Replies: 18

1.Express
as the product of 2 factors, where neither of them is 1.

2. Express as the product of 2 factors, where neither of them is 1. Do not express these 2 factors explicitly.

3. What does equal?

4. Find all integers where n! is a multiple of n^2.

5. If 3 numbers are chosen at random from first 1000 natural numbers,what is the probability that the three numbers are in G.P.? All numbers are distinct.

6. prove that is true for all non negative integers.

## #12 Re: Exercises » Mathematics Challenges, #1 » 2016-07-17 12:36:19

bobbym wrote:

Hi;

I do not agree.

Why assume x > y? The problem does not state that. And why combinations? x and y are two different variables, so order should count. I think that EVW has the correct two answers for the problem as stated.

Please Mathegocart be more specific which answer, he has 3 different answers, is the one you think is correct.

Where did that little guy go?

That was quite late at night for me, I believe now that EVW's answers are right.

## #14 Re: Exercises » Mathematics Challenges, #1 » 2016-07-17 02:38:37

bobbym wrote:

I think √  and x²  are  copied from top of this page and not LaTex.

That is precisely the point.

True but I was too lazy to put LATEX on the top. I will now.

Penguins are hard workers so they can not claim they are lazy. So what is it for 3? With replacement or not?

I meant to say without. Penguins are busy animals, surely.

## #15 Re: Exercises » Mathematics Challenges, #1 » 2016-07-16 03:18:44

I think √  and x²  are  copied from top of this page and not LaTex.

True but I was too lazy to put LATEX on the top. I will now.

## #16 Help Me ! » Confirmation of bike problem » 2016-07-16 03:17:00

Mathegocart
Replies: 3

Kai rides his bike up the hill to school and back every day. If he travels twice as fast downhill as up, and it takes 30 minutes round trip how far away is it from his school?
I don't believe that there is a solution with the given information.

## #17 Re: Exercises » Mathematics Challenges, #1 » 2016-07-16 01:41:38

bobbym wrote:

Hi;

For 3) with replacement or without? Also, you mean

We are going to have to teach you some latex. It is pronounced lah - tek?! Now ain't that just as weird as a two headed squirrel? Us bumpkins say lay-tex like the sap they make rubber from.

Bobbym, modus means method, and I already know LATEX.

## #18 Help Me ! » Silly origin problem » 2016-07-15 14:05:41

Mathegocart
Replies: 1

Which of these points are closest to the origin?
A.(-1,-1)
B.(.5,.5)
C.(.5,-.5)
D.(0,-1)
E(0,.5)
There is only 1 answer, apparently.
Wouldn't B and C be the nearest to the origin(having distance .25?)

## #19 Exercises » Mathematics Challenges, #1 » 2016-07-15 13:42:57

Mathegocart
Replies: 17

1. We have a unit square [0,1],[0,1]. I pick 2 random numbers from this unit square with uniform distribution. What is the average length  between these two numbers? What is the median length?  What is the modus??
2. Find the sum of the reciprocals of the triangular numbers.

3. I choose 2 integers from the set [1,100]. What is the probability that $\sqrt{xy} > x - y$

4.Does there exist a function f:R→R such that $f(f(x)) = x^2-2x$ for every real number x? Prove whether or not this exists.

5. Find all numbers x for which the equation where 3^x + 3^-x = 3.

## #20 Re: Help Me ! » olympiad problems » 2016-07-14 09:34:52

I need serious help on number 3

## #21 Help Me ! » olympiad problems » 2016-07-14 04:15:59

Mathegocart
Replies: 4

1. A train travelling 30mph reaches a tunnel which is 9 times as long as the train. If the train takes 2 minutes to clear the tunnel, how long is the train in feet?
first 2/60 = 1/30 of an hour, thus the train travels 1 mile. Thus the tunnel is 1 mile. 5280 miles divided by 9 = 586.6666 reperating, so the train is 586.6 feet.
2. If x - y + 2z, and x+z = y + t, and y + t+z, how many z's = x?
3. a athelete running 100 meters or 200 meters does not reach top speed until 40 miles. In a 200 meter race a certain runner's time is 5.4 secs and his time for 100 meter s is 10 secs.Assuming he maintains full speed from 40 meters to the end of the reae, what would be his time for 200 meters?

## #22 Help Me ! » Silly problem » 2016-07-12 15:10:30

Mathegocart
Replies: 3

In the following sequence of numbers. each number has one mode 1 thean the preceding number. 1,11,111,1111,11111.... Which is the tens digit of the sum of the first 30 digits in the sequence?

## #23 Exercises » Mathematical Problems #8 » 2016-07-10 13:44:28

Mathegocart
Replies: 2

1. Separate the product of the product of 999 and 7163 into sums that add to 999
example: 5 x 999 = 4995, 4 + 995 = 999.
2. Bobbym and Agnishom both leave Mathocity on their cars at the same time. Bobbym travels at a constant speed of 12 miles per hour and Agnishom at a constant 8 Miles per hour. Bobbym arrives at Sophopolis 2 hours before agnishom. How many miles is it from Mathocity to Sophopolis?
3. Find a 6 digit number whose numbers are l distinct such that when it is multiplied by 1, 2, 3 ,4, 5 or 6, the product contains the same set of digits.
4. When the Bobbym family went on vacation, mr bobbym traveled 4/9 of the distance at 40mph, 7/18 of the distance at 70mph, and the final 3- miles at 60mph. If there WERE NO STOPS, the entire trip took them X hours. find X.
5. Bobbym's water bill for every 30 days is \$16. For the next 30 days the sprinklers were on everyday for 15 minutes 4 times per day.. His water bill then increased to 184. For the next 3 days he will have his sprinkers on every other day and ONLY ONCE for 15 minutes. His water bill for these 30 days should be...
2A x AB = 1971, A =B, find a + b.
6.(1-1/3)(1-1/4)...(1-1/50) =?
7. (2^100 + 3^100) modulus 5 = ?
8. (20-19+18....+2-1)/(19-18....+3-2+1) =?

## #24 Help Me ! » Track question » 2016-07-10 09:50:13

Mathegocart
Replies: 25

1. A circular track is 1000 yards in circumference. Cyclists A B and C start at the same place and time at the following rates per minute, respectively, 700 YARDS, 800 yards, and 900 yards. What is the LEAST number of minutes it takes for all 3 to be back again?

## #25 Re: Exercises » Twisters, #6 Mathematics » 2016-07-07 15:00:13

Hi mathegocart,

They are both correct.