Q&A - P4 Math

[Michell0328]

Tessa exchanges $200 for some $5-notes and $2-notes. She has 5 more $5-notes than $2-notes. Find the number of $5-notes she has.

[Michell0328]

I believe this problem needs to be solved by Guess and Check Method. Since there are 5 more $5 note than $2 note, in its simplest form, there would be 6 $5 note and 1 $2 note. Using Guess and Check Method and making sure that the difference between $5 note and $2 note is kept at 5, the number of $5 note would be 30.

[Michaelia0816]

5xS5=$25

$200-$25=S175
$2+$5=$7
$175 divide $7=25
25+5=30
The answer is 30.

[Michell0328]

Michell wants to put an equal number of sweets into some bags.The total number of sweets she has is more than 50 but less than 90.If she puts 5 sweets into each bag,she has 4 sweets left.If she puts 8 sweets into each bag,she will need 1 more sweet.How many sweets does Michell have??

[Michaelia0816]

The answer is 79.

[Michaelia0816]

Use guess and check to solve.

[Michaelia0816]

Goodluck.

[MathIzzzFun]

Michell0328:

Michell wants to put an equal number of sweets into some bags.The total number of sweets she has is more than 50 but less than 90.If she puts 5 sweets into each bag,she has 4 sweets left.If she puts 8 sweets into each bag,she will need 1 more sweet.How many sweets does Michell have??

Hi

Note that is we add 1 more sweet to the total, the new total will be divisible by 5 & 8 ie the new total is multiples of 40.

Possible numbers of sweets = multiples of 40 less 1
Since number of sweets is between 50 & 90, the only possible answer = 80 -1 = 79

cheers.

[Tresille]

MathIzzzFun:

Tresille:

Hi, need your assistance.


John has a total of 20 apples and pears. If he exchanges every pear for 2 apples, she will have 28 apples. How many apples and pears does he have? Can we use model drawing to solve this qn?

Hi

using model drawing...

http://i39.tinypic.com/2dbw8km.jpg\">

cheers.

:thankyou: MathIzzzFun

[Tresille]

Xiao Hu:

Zack7:

[quote=\"Tresille\"]Hi, need your assistance.


John has a total of 20 apples and pears. If he exchanges every pear for 2 apples, she will have 28 apples. How many apples and pears does he have? Can we use model drawing to solve this qn?

let x be pears
let y be apples

x + y = 20
2x + y = 28

20-x = 28 -2x
x = 8 pears
y = 12 apples



it is possible to use models to solve this question
but you have to do it to scale. or have a relative scale
like 1cm to 1 unit. but it is not an efficient way to do this sort of questions.

in fact , i just need to use logic to be able to solve this question. logic is the best approach for simple cases like these.
if 1 pear becomes 2 apples, then that would mean every pear i change to apple will yield me a net of +1

so if i have 28 as a new total, where did the 8 extra came from? it would mean i have a net of +8. then, it would mean i have changed 8 pears.

if i had 38 as a new total, it would mean 38-20 = 18, which means i have changed 18 pears and so on...

Hi Tresille,
For P4 level and for this question, other than Guess & Check strategy/method, can use the Supposition/Supposition & Tabulating & look-for-a-pattern strategy. Please see page 48 on one of post by Tianzhu. You can search \"\"4)There were 50 children in Xie Ming Ming’s party\". Tianzhu had given quite a lot of such questions with solutions thrown in. I encourage you to take a look.

Hope it helps.
XiaoHu.[/quote]Thanks, XiaoHu! I'll refer to Tianzhu's solution and try to explain to my DS.