# Thread: A question to explain to a 10 year old

1. ## A question to explain to a 10 year old

Hi Here is a question to explain to a 10 year old . I don't know what to do?

In a cafe 1 burger and 2 drinks cost £2.80
Same cafe 2 burgers and 5 drinks cost £6.10
Find cost of 1 burger and 1 drink.

Please explain in a simplyfied way so she can calculate similar questions in an exam coming up

Thanks

Dee

2. Originally Posted by dee@landspace.co.uk
Hi Here is a question to explain to a 10 year old . I don't know what to do?

In a cafe 1 burger and 2 drinks cost £2.80
Same cafe 2 burgers and 5 drinks cost £6.10
Find cost of 1 burger and 1 drink.

Please explain in a simplyfied way so she can calculate similar questions in an exam coming up

Thanks

Dee
$\displaystyle x =$price of burgers
$\displaystyle y =$price of drinks

$\displaystyle x+2y = 2.8$
$\displaystyle 2x+5y = 6.1$

Rearrange the first equation to get $\displaystyle x = 2.8-2y$, then put that into the 2nd equation:

$\displaystyle 2(2.8-2y)+5y=6.1$

Solve for y. When you have a value for $\displaystyle y$, put it back into the first equation to get a corresponding value for $\displaystyle x$.

$\displaystyle 5.6 - 4y + 5y = 6.1$

$\displaystyle y = 6.1-5.6 = 0.5$

$\displaystyle x = 2.8-2y$

$\displaystyle x = 2.8-2(0.5) = 1.8$

3. Originally Posted by dee@landspace.co.uk
Hi Here is a question to explain to a 10 year old . I don't know what to do?

In a cafe 1 burger and 2 drinks cost £2.80
Same cafe 2 burgers and 5 drinks cost £6.10
Find cost of 1 burger and 1 drink.

Please explain in a simplyfied way so she can calculate similar questions in an exam coming up

Thanks

Dee
here's how I would try to explain to a 10 year old ...

1 burger and 2 drinks cost £2.80

double that ...

2 burgers and 4 drinks cost £5.60

you also know that 2 burgers and 5 drinks cost £6.10

from the last two statements, one can determine that the extra 1 drink costs £0.50

finally, since 1 burger and 2 drinks cost £2.80, 1 burger costs £1.80

4. Here is a simpler approach so that a 10 year old can understand it better. As he/she might not understand simultaneneos equations.

Since 1 burger and 2 drinks cost £2.80
Then 2 burger and 4 drinks cost £5.60 ( multiply by 2 )

Since 2 burgers and 5 drinks cost £6.10 is given
We just have to minus £6.10 - £5.60 = £0.50 to get the cost of the drink as 2 burgers and 5 drinks minus 2 burger and 4 drinks = 1 drink

Since we have the cost of the drink we can easily calculate the cost of 1 burger
1 burger and 2 drinks cost £2.80
1 burger + 2(0.50) = 2.80
1 burger = 2.80 - 1.00 = 1.80

Hope it helps.

Originally Posted by dee@landspace.co.uk
Hi Here is a question to explain to a 10 year old . I don't know what to do?

In a cafe 1 burger and 2 drinks cost £2.80
Same cafe 2 burgers and 5 drinks cost £6.10
Find cost of 1 burger and 1 drink.

Please explain in a simplyfied way so she can calculate similar questions in an exam coming up

Thanks

Dee

5. Hello, Dee!

Here is a visual approach to skeeter's excellent solution.

In a cafe 1 burger and 2 drinks cost $2.80 Same cafe: 2 burgers and 5 drinks cost$6.10
Find cost of 1 burger and 1 drink.

We are told that: .$\displaystyle B\,D\,D \;=\;280$ .1]

One burger and two drinks cost 280.

Double the order: .$\displaystyle B\,B\,D\,D\,D\,D \;=\;560$ .[2]

Two burgers and four drinks cost 560.

We are also told that: .$\displaystyle B\,B\,D\,D\,D\,D\,D \;=\;610$ .[3]

$\displaystyle \text{From {\color{blue}[2]}, we have: }\;\underbrace{B\,B\,D\,D\,D\,D}_{\text{This is 560}}\,D \;=\;610$

. . Hence: .$\displaystyle D \:=\:50$

Then [1] becomes: .$\displaystyle B \:50\:50 \:=\:280$

. . Hence: .$\displaystyle B = 180$

Therefore, a burger costs $1.80 and a drink costs 50$\displaystyle \rlap{/}c\$