Maths year 11

Think about what numbers would round to give you 2.7. You are rounding to 1 d.p. in this case rather than in integer.

Omg please don't waste your time writing notes in maths. Have a concept explained to you then do questions to consolidate your knowledge whilst the explanation is fresh in your head. Then over the weekend or the next week, do more questions over and over. Practice is what's key in maths not pretty notes

I'm not making pretty notes? I'm doing questions on a book so I can remember the concepts and I'm using them to do other questions similar to that?
I understand best with colour that's why I use colours?

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Yes those numbers will round to 2.7. But what about 2.65 and 2.7499999....?

They round to 8

And 99999999 can be rounded to 2. 8

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Not quite. If you ignore the decimals for a moment and imagine that you are rounding to 270, your two bounds will be 265 and 275. Now add a decimal point in each of those then you get the bounds of 2.70 being 2.65 and 2.75. (2.7=2.70)

Not quite. If you ignore the decimals for a moment and imagine that you are rounding to 270, your two bounds will be 265 and 275. Now add a decimal point in each of those then you get the bounds of 2.70 being 2.65 and 2.75. (2.7=2.70)

Yes but they also could round to 3?

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Ignore the 3. You are focusing on decimals to 2 d.p. around 2.7 which itself rounds up to 3 anyway so that's insignificant. Since we know LB is 2.65 and UB is 2.75, and it's asking for longest length, it would be the upper bound.

Oh I'm going out so is it okay if you can make questions like this please . About 5
Easy first x

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I'm not RDKGames, but any practice is good practice! Here are 5 questions:

1) A pencil is 12cm long, to the nearest cm. What are its maximum and minimum possible lengths?

2) The population of the UK is 64 100 000, to three significant figures. What is the minimum population of the UK?

3) A boat travels 21.5 km, to the nearest 0.5 km. What is the furthest it might have travelled?
(Be careful, this is asking to the nearest 0.5km, not to the nearest 0.1km - a question like this came up in my IGCSE Maths exam last May [2016]).

4) A circle has radius 5cm, to the nearest cm. What is the greatest area and smallest circumference that this circle might have? (Leave your answers to 3 significant figures).

5) *Challenging* Robert has a solid metal cube of side length 25cm, to two significant figures. He melts the cube and makes some spheres, each with a radius of 2.5 cm, to the nearest 0.5 cm. What is the maximum number of spheres that Robert could have made? (A question very similar to this came up in my IGCSE Maths exam this summer, so this is a good indication of the most difficult bounds question you could get - note I did Edexcel IGCSE).

I hope you enjoy the questions; feel free to ask for hints, and I (or someone else) will be willing to help!

Ignore the 3. You are focusing on decimals to 2 d.p. around 2.7 which itself rounds up to 3 anyway so that's insignificant. Since we know LB is 2.65 and UB is 2.75, and it's asking for longest length, it would be the upper bound.

Did the first one unsure about the second one?

Btw thank you so much for the questions


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I don't understand when it says to the nearest 0.5km, population is..... 3 sf?

Radius of 5 to the nearest cm? ?

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OK, if you have 64 100 000 to 3 significant figures, what other numbers would round to it to 3 significant figures?

For example, would 64 110 000 round to 64 100 000? What about 64 090 000?

An easier way to approach it might be to take off all the excess zeros for now, so you have the number 641. What is the lower bound of 641, if this is only accurate to 3 sig figs? Then, move that back up to the millions.

Lower bound - 640.95?

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