Q&A - P4 Math

[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.

[warriortemujin]

Thanks for sharing.

[Charnic]

Pls help urgently. Thanks



Siti went shopping with some money. She spent $65 in shop A
and 3/5 of the remainder in Shop B.
She had $20 left.
Find the amount of money she had at first.

[zeemimi]

CNS:

Pls help urgently. Thanks



Siti went shopping with some money. She spent $65 in shop A
and 3/5 of the remainder in Shop B.
She had $20 left.
Find the amount of money she had at first.

2u = $20
1u = $10
Hence she spent 3u = $30 at shop B

At first = 65 + 30 + 20 = 115

[Charnic]

That is what i that but the answer provided but t is 106. Possible ?

[MathIzzzFun]

CNS:

That is what i that but the answer provided but t is 106. Possible ?

Hi

where is the question from ? It is likely the answer given was based on $56 spent on Shop A.

cheers.

[Charnic]

School homework, maybe is just a typo mistake by t. I will stick to my anw of 115.

[Michaelia0816]

zeemimi:

CNS:

Pls help urgently. Thanks



Siti went shopping with some money. She spent $65 in shop A
and 3/5 of the remainder in Shop B.
She had $20 left.
Find the amount of money she had at first.

2u = $20
1u = $10
Hence she spent 3u = $30 at shop B

At first = 65 + 30 + 20 = 115

Hi I am a p6 student and may be able to help u, I also got a brother in P4
and a smart mum

My method:
2/5 of the remainder------$20
1/5 of the remainder------$10
5/5 of the remainder------$50
$50+$65= $106

[Michaelia0816]

If u need MD tell me

[BigDevil]

Michaelia0816:

$50+$65= $106

Shouldn't that be $115??