percentages

11 Plus Maths – Preparation and Information

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Here we go again
Posts: 13
Joined: Thu Jun 05, 2008 10:20 am

percentages

Post by Here we go again »

What is the easiest way to work this one out:

Mrs Jones earns £21,000 and gets a 7.5% pay rise. What is her new salary?
(from Bond 10-11+)

Any help would be appreciated.
T.i.p.s.y

Post by T.i.p.s.y »

If using a calculator it would be 21000 x 1.075 = 22575

and if not 75/1000 x 21000 = 1575 and then add it on to 21000
chad
Posts: 1647
Joined: Tue Dec 13, 2005 1:49 pm
Location: berkshire

Post by chad »

In my head I would say 1% is 210

210 x 7 = 1470

add on 1/2 of 210 - 105

therefore 1575 is 7.5%

add on to salary giving 22575
kentish maid
Posts: 66
Joined: Thu Jan 10, 2008 10:53 am
Location: kent

Post by kentish maid »

i'd say

10% =2100

therefore 5 % = 1050

therefore 2.5 % =525

7.5% = 525 + 1050 =1575

I guess which method you chose depend on what calculation your more comfortable with.
Here we go again
Posts: 13
Joined: Thu Jun 05, 2008 10:20 am

Post by Here we go again »

Thanks everyone.

I was trying to do it as a sum: times by 7.5, divide by 100 and add to salary but the figures get a bit messy for a ten year old.
She likes to do things in hear head using mental maths so I think she would prefer to do it this way. I guess this is really what they are looking for with this type of question anyway.
SunlampVexesEel
Posts: 1245
Joined: Fri Jul 06, 2007 9:31 pm

Re: percentages

Post by SunlampVexesEel »

Here we go again wrote:What is the easiest way to work this one out:

Mrs Jones earns £21,000 and gets a 7.5% pay rise. What is her new salary?
(from Bond 10-11+)
Any help would be appreciated.
I would urge Mrs Jones to show some wage constraints as this will only fuel inflation (and make me jealous)

10% of 21k is 2100

7.5% is 3/4 of 10%

2100/2=1050 1050/2=525

525 * 2 = 1050 + 525 = 1575

add on the original

22575

Regards
SVE
Animis opibusque parati
Here we go again
Posts: 13
Joined: Thu Jun 05, 2008 10:20 am

Post by Here we go again »

LOL Yes, 5% would be easier to compute and more like the real world. Maybe the question should be 'MP earns £200,000 a year and gets a 15% pay rise plus £15,000 bonus. What is his new salary? :)
Primemaths
Posts: 2
Joined: Fri Jun 27, 2008 2:22 pm

Post by Primemaths »

kentish maid wrote:i'd say

10% =2100

therefore 5 % = 1050 [ halve the 10% -i.e. divide by 2]

therefore 2.5 % =525 [ halve the 5% - divide by 2]

7.5% = 525 + 1050 =1575 [ 7.5% = 5% + 2.5%]

I guess which method you chose depend on what calculation your more comfortable with.
I agree. This method tends to be easier. I have added brief explanations.
T.i.p.s.y

Post by T.i.p.s.y »

I agree that some of these methods may be easier than other methods, but what if the figure was 18.76% for example? You couldn't then use these methods as easily so is it not better to have one method for all percentages, and I don't necessarily mean my method?! :)
Primemaths
Posts: 2
Joined: Fri Jun 27, 2008 2:22 pm

Post by Primemaths »

T.i.p.s.y wrote:I agree that some of these methods may be easier than other methods, but what if the figure was 18.76% for example? You couldn't then use these methods as easily so is it not better to have one method for all percentages, and I don't necessarily mean my method?! :)
Correct. However, most of the questions in 11+ and common entrance are phrased in such a way as to not require a calculator. So you are more likely to find whole percentages or half or 3/4 rather than xx.76. Remember also the kids have between 60 and 90 seconds to do the questions.
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