Math Is Fun Forum

You're welcome.

Good luck with the exam.

Bob

hi Aartt,

Why don't you work through the Maths Is Fun algebra section that starts at http://www.mathsisfun.com/algebra/introduction.html

Bob

hi Aartt,

Very good.  I got 6.35903..... so I rounded up to 6.36 cm.  Take care with the rounding!

Another one below.  Say when you feel you've had enough trig and want to move on.

Bob

hi Aartt,

Ok, here's one

Bob

hi Aartt,

Sorry I've not contributed to this thread for a while.  I was out for a whole day and then, when I looked, you seems to be progressing well with your trig. 

Now you seem to be hung up on rounding off.

So, maybe a little lesson in that will help.

I'm going to look at the decimal number 1.817

Here's a picture that shows where it is on the number line.

Firstly, the gap between 1 and 2 is divided into tenths.  Our number is over 1.8 but under 1.9

Then, the diagram is magnified by x 10 so you can see the hundredths.

Our number is between 1.81 and 1.82

Then the diagram is magnified by x 10 again to show the thousandths.

Our number can now be shown exactly as 1 unit, 1 tenth, 8 hundredths and 7 thousandths.

Now for the rounding off.

If you truncate the number you just chop off unwanted digits so you'd get 1.81

But the diagram shows that 1.817 is nearer to 1.82 so this is the correct thing to write if you are rounding.

I've seen you write the rule for this in post 99

But why this rule?

Because you're looking to see which way is nearer;
4 and below means 'to the left' is nearer;  this is ROUNDING DOWN
above 4 means 'to the right is nearer;  this is ROUNDING UP.

There are many ways to ask someone to round off:

Give answer to 2 decimal places
Give answer to 3 significant figures
Round to the nearest whole number
etc etc.

Does that help?

Footnote.  It's 3.16am, here in England.  I woke up and couldn't sleep so I thought I'd have a look at MIF.

I think there's a big time difference between us, which is why you sometimes post and then wonder why there's no reply for a while.  Tell me what your screen says for the time I posted this and we can work out the time zone difference.
Bob

Hi MathsIsFun

Money Master loads and runs. I only tried one option.  It looks like it's got loads of potential.  Thanks.

Got hexxagon loaded but couldn't do anything with it.  I'm using IE7.  I could toggle between the games options so I chose 'against the computer'.  Board appeared but I couldn't move a piece.  Did I miss the instructions?

Bob

Hi again

How about:

Consider

What is it equal to?

Then use what you are given to show what

is equal to.

Use this to show

And then to the required result.

Can you fill in the gaps?

Bob

So do you want another one?

Bob

hi Au101,

That's weird.  I didn't see a diagram so I assumed the lamina was lying flat against the plane.

Having read part B, I'm suspecting this may have been a false assumption.

Any chance of getting a diagram into a post?

Bob

hi AU101,

6 marks does seem a lot for a simple pythagoras and two easy divisions, but I cannot see a way to make this question more difficult to do.  So well done! Have 6 marks!

I'm guessing that there a part (b) in which you have to do something involving theta.

Perhaps the person who made up the question thought "Part b is the bit I really want to test, so I'll give an easy part a just to get them warmed up"

Bob

hi Aartt,

Don't be depressed about it.  MIF help will get you there!

This is how I get my students to do these:

(i)  Check you have got a right angled triangle.  (In our exams it's common to give an isosceles triangle.  The students must cut it down the line of symmetry before they can use trig.)

(ii)  Decide what you know:  angle?  adjacent?  opposite?  hypotenuse?  and what you are asked to calculate.

(iii)  Choose SOH, CAH or TOA as appropriate.

(iv)  Decide the exact form of the formula.

(v)  Substitute numbers and find the required value.

(vi)  Consider, 'is this a sensible value for this problem?'

Here's an example:

See diagram below.

(i) Yes, it has a right angle.
(ii)  I know Adjacent and Hypotenuse and want the angle.
(iii) I'll use CAH
(iv)  So

(v)  so

so x = 36.9

(vi)  8 is not too far under 10 so the angle is probably under 45.  36 seems reasonable.

Would you like to try this one:

see second diagram

Bob

Hi bobbym,

I never knew about the

!!:)!!

Maybe I should re-consider my life-plan.

Now about this cat. 

Is the adjacent still 100ft and the angle 37.  Because I then make it hypotenuse = 125.2ft.

Hint for you and Aartt.

(i) bobbym.  Post a fresh diagram so Aart can see what you're giving for each problem.

(ii) Aartt  Say whether you are using SOH, CAH or TOA each time, then exactly what calculation you are doing, finally your answer.

That way it will be clear where you are going wrong. (or hopefully, not going wrong at all!    )

Bob