Just looking now, please stay on for a mo

Bob

the quistion are (C) 28.243 / 2.6 to 2 dec places
                        (D) 0.25 / 4.5 to 2 sig.figures
So how do you do these then? can you show me and send message back now please?

the answers are (C) 10.8626931 and (D) 0.055555555 are they right or not? let me know please?

hi Mandy,

Ok both calculations are correct.

But they have to be rounded off.

example.  The Electricity company does an accurate calculation for you bill and gets £85.862775

But you cannot pay this exactly as there are no coins that small!  It has to be rounded to the nearest penny or 2 decimal places.

So they call it £85.86 and forget the rest.

That's how rounding works.

So, look at the number line below.  I have shown the bit between 10.86 and 10.87

Your number is 10.8626931.

Look at the three coloured lines, red, green and black.  Which one marks the correct position for 10.8626931 ?

If you are not sure, go to the Zoomable Number Line at

http://www.mathsisfun.com/numbers/number-line-zoom.html

and move to show the number line like I have.

Then zoom in until 10.862 is showing.  Now answer the question about the coloured lines.

Bob

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Are you just guessing?

Have you looked at the Zoomable Number Line page?

Bob

No.  You are not right.

Look at my picture below.

I have zoomed in to show where 10.862 lies on the line.  The 2 gives you the clue.

10.862.... is much closer to 10.86 than it is to 10.87.

So you should have said the green line.

That means the answewr to the rounding off question is 10.86

Do you understand?

Bob

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Before we go on, let’s do some practice with rounding to 2 decimal places

For each question,  use the Zoomable Number Line to look at the number.

Decide which number it is nearer to.  That is the correct rounding off.

Q1)   10.573  (nearer to 10.57  or nearer to 10.58 ? )

Q2)   15.237 (nearer to 15.23  or nearer to 15.24 ? )

Q3)   7.881  (nearer to 7.88  or to 7.89 ? )

Q4)   45.047134  (nearer to 45.04  or to 45.05 ? )

Q5)  7.555555 (nearer to 7.55 or to 7.56 ? )

Bob

Have a look at

http://www.mathsisfun.com/numbers/rounding-tool.html

This will allow you to set the number of decimal places to 2.

You can type a number, click => to see the computer's answer to compare with yours.

Bob

hi Mandy

Q1) 10.57      Correct, well done!
(Q2) 15.237   Not correct.  Answer should be 15.23 or 15.24
(Q3) 7.881     Not correct. Answer should be 7.88 or 7.89
(Q4) 45.05    Correct, well done!
(Q5) 7.55      Not correct.  The number in the question is just over half way between 7.55 and 7.56

After you have corrected these please practise some more at

http://www.mathsisfun.com/rounding-numbers.html

Scroll down to the bottom of this page and you will find 10 questions for you to try.

Keep trying them until you can get 10/10

Bob

hi Mandy

Q2) is 15.24    Correct, well done!
(Q3) is 7.88     Correct, well done!
(Q5) is 7.555   Not correct.  All of these questions asked for 2 decimal places.  Your answer still has 3.
The number 7.555555 lies just over half way between 7.55 and 7.56  When you round off, you have to chose the number which is nearest.
So which is it nearer to,   7.55 or 7.56 ? 

Bob

Hurray!  All correct.  But I have suggested you do some practice on rounding.  Also there's still the fractions.

By my reckoning you should be able to correct everything in Q1 and Q2 from your assignment.

Get the above topics sorted and then we'll move on to Q3.

Bob

The times table program is available on my website.  I'll email you details.

Bob

Here's the latest screen shot.

Bob

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