All Answers

#7

+118725

0

That is great - I am glad that you like it here Happy :)

MelodyJan 5, 2015

#6

+7188

+5

Thanks Melody! Ienjoy it here!

happy7Jan 5, 2015

#1

+118725

+5

the angle of elevation from a point 118 meters from the base of a tower to the top of the tower is 69.8 degrees. find the height of the tower

I would like to help you work this out for yourself.

Where do you think those numbers belong using my pic below?

Remember, angle of elevations is from the horizontal looking up.

T for top, b for bottom

MelodyJan 5, 2015

#1

+5

thanks guys! I got it!

GuestJan 5, 2015

#392

+118725

+8

@@ End of Day Wrap Mon 5 /1/15 Sydney, Australia Time 10:30pm ♪ ♫

Hi everyone,

I have not posted a wrap for a few days. I have been preoccupied I am sorry.

There have been many great questions and most of these were answered very well by Tetration, CPhill, ororen1909, NotTheBestMathMaster, rajaae, Kitty<3, Alan, and geno3141. Thanks all

Now there were many good post. Here are some of them.

Every maths mover must be able to find something interesting in there.

1) Interesting domain question.

http://web2.0calc.com/questions/what-is-the-domain-of-this-function-sqrt-x-3-x-2#rr1

2) Interesting trig. Unit circle and exact values. Melody

http://web2.0calc.com/questions/evaluate-each-expression-without-using-a-calculator-and-write-your-answers-in-radians

3) What are permutations and combinations ? Melody

http://web2.0calc.com/questions/how-many-possible-combinations-are-there-for-a-deck-of-cards

4) A really good rates and volume question. Melody

http://web2.0calc.com/questions/help-with-problem_1#rr5

5) Physics Thanks Alan

http://web2.0calc.com/questions/two-5-kg-masses-are-attached-to-opposite-ends-of-a-long-massless-cord-which-passes-tautly-over-a-massless-frictionless-pulley-the-upper-mas

6) Some geometry. Chris would like someone to check his answer but he thinks it is good. Thanks Chris.

http://web2.0calc.com/questions/the-area-of-a-rhombus-is-250-and-one-of-the-angles-is-37-deg-27-what-is-the-length-of-each-side

7) All in fun :)) NotTheBestMathMaster, Melody, Nauseated, Alan and CPhil.

http://web2.0calc.com/questions/how-many-times-would-a-mole-of-shoe-strings-16cm-long-stretch-from-earth-to-the-moon

8) Formula for triangular numbers Thanks Alan and Chris

http://web2.0calc.com/questions/how-do-you-work-out-the-formula-nth-term-for-the-triangular-number-sequence

9) Parabola question, different from the norm - Thanks Alan

http://web2.0calc.com/questions/the-vertex-of-the-parabola-is-on-the-line-y-20-the-y-intercept-is-15-and-3-is-a-zero-of

10) This is not a high level question but I liked it. (percantages) :)

http://web2.0calc.com/questions/a-chemist-needs-a-solution-of-tannic-acid-70-pure-how-much-distilled-water-must-he-add-to-5-gallons-of-acid-which-was-90-pure-to-obtain-t

11) A couple of revision/learning sites suggested by Chris

http://web2.0calc.com/questions/so-i-am-currently-taking-solid-mensuration-in-college-i-am-having-a-hard-time-to-pick-up-and-learn-the-lessons-were-currently-at-quadrilat

12) Proof by Induction Thanks Chris

http://web2.0calc.com/questions/math-induction

That is it for today. Thanks everyone

♫♪ ♪ ♫ ♬ ♬ MELODY ♬ ♬ ♫♪ ♪ ♫

MelodyJan 5, 2015

#203

+118725

0

Tues 6/1/15

1) This is an old one but many people have been away on holidays and I'd really like people to read my new years message. It is just intended as a thank you to you all.

This is the wrap address but it links to mine and Rosala's new year messages. :)

http://web2.0calc.com/questions/all-questions-answered-to-this-point#r390

2) I am still thinking about this area question

http://web2.0calc.com/questions/how-to-you-approach-solving-the-moving-sofa-problem-for-rectangles-only-but-given-hallway-widths-a-and-b-not-width-1-and-1-as-in-the-orig

3 ) Imaginary numbers $$\sqrt[4]{-1}$$ I liked this one.

http://web2.0calc.com/questions/square-root-of-i

♫♪ ♪ ♫ ♬ ♬ MELODY ♬ ♬ ♫♪ ♪ ♫

MelodyJan 5, 2015

#2

+118725

0

I posted this some time back. Only happy7 commented.

Did no-one else find it worthy of comment?

Anyway, I stumbled across it and I thought I would bump it and see if I get any response before I let it retire into oblivion.

MelodyJan 5, 2015

#1

+118725

+5

find (the average of the x values by adding them together and dividing by 2, the average of the yalues)

MelodyJan 5, 2015

#1

+118725

+5

$${\frac{{\mathtt{1\,507.96}}}{{\mathtt{\pi}}}} = {\mathtt{479.998\: \!575\: \!969\: \!708\: \!981\: \!1}}$$

so

1507.96= 480$${\mathtt{\pi}}$$ (approx)

MelodyJan 5, 2015

#1

+118725

+5

100%-40%=60%

MelodyJan 5, 2015

#3

+118725

0

This is one I want to look at properly. If only there were infinite hours in each day :)

THEN we could all procrastinate forever and it would not make one iota of difference :)

MelodyJan 5, 2015

#1

+118725

+5

Now that would depend upon what s is :)

MelodyJan 5, 2015

#1

+118725

+5

If you times any number by 0 you get 0.

MelodyJan 5, 2015

#1

+118725

+5

A polygon with 3 sides.

MelodyJan 5, 2015

#1

+118725

+5

90% of 5 gallons = 0.9*5 = 4.5 gallons

So the original mixture contains 4.5 gallons of acid and the and 0.5 gallons of water.

Now we need to know 70% of what equals 4.5 gallons

0.70x=4.5

x=4.5/0.7

x=6.4286 gallons (correct to 4 dec places)

We already have 5 gallons

6.4285-5=1.4285 gallons

So you will need to add 1.4285 gallons of water.

MelodyJan 5, 2015

#4

+33666

+5

I agree that Chris's analysis is correct (apart from the bit that says "divide both sides by 32" - this should say "divide both sides by 16"!!)

.

AlanJan 5, 2015

#1

+33666

+5

mass of neutron/mass of electron = 2*10^-24/(9*10^-28)

$${\frac{{\mathtt{2}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{\left(-{\mathtt{24}}\right)}}{\left({\mathtt{9}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{\left(-{\mathtt{28}}\right)}\right)}} = {\mathtt{2\,222.222\: \!222\: \!222\: \!222\: \!222\: \!2}}$$

so d is closest.

.

AlanJan 5, 2015

#1

+33666

+5

The general equation for a parabola can be written as: (x - h)² = 4a(y - k) where (h, k) are the coordinates of the vertex.

Since we are told that y = 20 at the vertex, then we know immediately that k = 20.

The y-intercept occurs where x = 0, so we have: (0 - h)² = 4a(15 - 20) ...(1)

A zero of the equation means the value of x where y = 0, so we also have: (3 - h)² = 4a(0 - 20) ...(2)

Can you use equations (1) and (2) to find two sets of values for h and a?

.