11 Plus Exams Forum

Good Morning

Can anyone please explain the following as DD does not understand these two questions at all.

1. Leatown is holding it's annual fun run.
Medals are given to all the finishers
The cost, in pence, of n medals is given by the expression

300 + 20n

How much will 150 medals cost?

The answer pack states the answer is £33.00.


2. Which one of these expressions is equivalent to 2(n+1)?

2(n+2)-1
2n+1
2n+2
2(n-1)+2
2(n+3)-2

The answer pack states that the answer is 2n+2

As you can see, there is a pattern emerging and Dd can not make sence of any questions that contain a letter. Any help would be appreciated.

Thanks in advance
Ann

I think it may be a typing mistake in question?

It says the cost of 'n' medals (in pence) is 300+20n
hence the cost of 150 medals = 300 + (20*150)
= 300 + (300)
= 600
= £6?

I think it may be a typo and should be

3000+20n
3000+(300) = 3300
Convert to £ by dividing by 100...
that would come to £33???

I would get him to use an example on the second question

Basically 2(n+1) is directing you to add one to the base number then multiply by 2

2n+2 is directing you to multiply the base number by two then add 2

SO the basic concept is in the first you add 1 then multiply by 2
In order to achieve the same then you can mutliply the base number by 2 but because you havent yet added the one you would have to double it.

Use any number to illustrat

3 = 2(3+1) = 2x4=8
3 = 2x3+2 = 6+2 = 8

17 = 2(17+1) = 2x18 = 36
17 = 2x17+2 = 34+2 = 36

Hope that helps

1. Leatown is holding it's annual fun run.
Medals are given to all the finishers
The cost, in pence, of n medals is given by the expression

300 + 20n

How much will 150 medals cost?

This type of question just requires you to substitute (replace) 'n' by the number of medals required ie 150

So you need to calculate 300 + (20 x 150)

2. Which one of these expressions is equivalent to 2(n+1)?

Something outside a bracket multiples everything inside it so 2(n+1) means 2 x (n+1) which is 2xn and 2 x 1 ie 2n + 2

Thanks Guest55, I will go over with DD at the weekend.

Generally speaking, where questions have an element of them represented by a number, should the answer always involve a bracket?

Thank you scouselover, unfortunately maths is not my strongest point!

scouselova wrote:I think it may be a typing mistake in question?

It says the cost of 'n' medals (in pence) is 300+20n
hence the cost of 150 medals = 300 + (20*150)
= 300 + (300)
= 600
= £6?

I think it may be a typo and should be

3000+20n
3000+(300) = 3300
Convert to £ by dividing by 100...
that would come to £33???

20 × 150 = 3000 not 300

3000 / 100 = 30 (i.e.£30).

The question as posted works correctly.

kal12003 wrote:Thanks Guest55, I will go over with DD at the weekend.

Generally speaking, where questions have an element of them represented by a number, should the answer always involve a bracket?

Sorry, I'm not sure what you mean.

You say your dd has difficulty at sums with letters in. To begin try and get her to see the letter as a box where you are trying to find the number in the box.

Then in the first question you are told what number is in the box and have to substitute this in.