Ascending order mix of decimals and fractions

11 Plus Maths – Preparation and Information

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fatbananas
Posts: 1411
Joined: Mon Mar 08, 2010 2:03 pm

Ascending order mix of decimals and fractions

Post by fatbananas »

Hello,

When DS has been ordering decimals or fractions, he's been taught to change them all to the same denominator (for fractions), or put them in tenths, hundredths columns etc (for decimals). However, neither he, nor I :oops: , can find a way to get some 'commonality' (ie the same denominator, or turning into decimals) for the following fraction/ decimal mix (WITHOUT using a calculator). Can anyone help? And, can anyone tell me if this mix would appear in an 11+ GS exam?

0.85, 4/5, 5/8
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mystery
Posts: 8927
Joined: Tue Jul 21, 2009 10:56 pm

Re: Ascending order mix of decimals and fractions

Post by mystery »

I guess I'd say that 4/5 is 8/10 so is 0.8, and that 1/8 is 0.125 (worth learning by heart) so 5/8 is 0.625 - then it is straightforward. I think also one might just have a "feel" for 5/8 being less than 8/10 --- it just "looks" closer to one half.

I would have thought that could be a GL assessment maths question.
leanmeamum
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Joined: Sat Dec 03, 2011 4:14 pm

Re: Ascending order mix of decimals and fractions

Post by leanmeamum »

4 divided by 5 gives a decimal answer of 0.8 and 1 divided by 8 would give you 0.125.

You can use long division or 'bus stop' methods to change fractions to decimals
fatbananas
Posts: 1411
Joined: Mon Mar 08, 2010 2:03 pm

Re: Ascending order mix of decimals and fractions

Post by fatbananas »

:oops: Ahem ... seems obvious now ... :oops: Thanks Mystery and Leanmeamum!
Seize the day ... before it seizes you.
Proud_Dad
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Re: Ascending order mix of decimals and fractions

Post by Proud_Dad »

mystery wrote:I guess I'd say that 4/5 is 8/10 so is 0.8, and that 1/8 is 0.125 (worth learning by heart) so 5/8 is 0.625 - then it is straightforward. I think also one might just have a "feel" for 5/8 being less than 8/10 --- it just "looks" closer to one half.

I would have thought that could be a GL assessment maths question.
One way to get a feel of 5/8, is to think that 6/8 = 3/4 = 0.75.

So 5/8 < 0.75, so must be the smallest.
Guest55
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Joined: Mon Feb 12, 2007 2:21 pm

Re: Ascending order mix of decimals and fractions

Post by Guest55 »

You only need to change them into the same denominator if you cannot judge their size or position on a number line in relation to each other.
fatbananas
Posts: 1411
Joined: Mon Mar 08, 2010 2:03 pm

Re: Ascending order mix of decimals and fractions

Post by fatbananas »

Guest55 wrote:You only need to change them into the same denominator if you cannot judge their size or position on a number line in relation to each other.
DS doesn't seem to be able to do this. Which particular fraction sizes should he know off by heart? 1/4, 1/2, 3/4, various eighths, sixteenths?
Seize the day ... before it seizes you.
Guest55
Posts: 16254
Joined: Mon Feb 12, 2007 2:21 pm

Re: Ascending order mix of decimals and fractions

Post by Guest55 »

Once you can order quarters then eight should be simple and sixteenths ...

Look at a fraction wall it can help some children 'see' the fractions in order.
SleepyHead
Posts: 484
Joined: Thu Oct 18, 2012 10:41 am

Re: Ascending order mix of decimals and fractions

Post by SleepyHead »

Think it's worthwhile memorizing the usual 1/2 , 1/4 , 3/4 as Guest55 says eights and sixteenths can be worked out, so other ones to memorise IMO are

1/3, 1/8 (meaning that you can work out sixths too if need be)
daddylonglegs
Posts: 66
Joined: Mon Sep 10, 2012 9:44 pm

Re: Ascending order mix of decimals and fractions

Post by daddylonglegs »

Probably not the best way to do this example, but if you wanted to get the same denominator (i.e. 40), I would do the following:

0.85 = 85/100 = 17/20 = 34/40

4/5 = 32/40

5/8 = 25/40
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