Q&A - P3 Math

[tracywham]

hello, i need help on this question (with model drawing will be greatly appreciated):


Siti had 6 times as many apples as David at first. After Siti had given 450 apples to David, they had an equal number of apples.

a) Find the number of apples David have at first.

b) David gave away some apples and had half the number of apples
Siti had. How many apples did David give away?

[jieheng]

tracywham:

hello, i need help on this question (with model drawing will be greatly appreciated):


Siti had 6 times as many apples as David at first. After Siti had given 450 apples to David, they had an equal number of apples.

a) Find the number of apples David have at first.

b) David gave away some apples and had half the number of apples
Siti had. How many apples did David give away?

At first
S [2u][2u][2u][2u][2u][2u] --> (12u)
D [2u]

After Siti had given 450 apples to David, they had an equal number of apples.
S [2u][2u][2u][1u] --> (7u)
D [2u][2u][2u][1u] --> (7u)

12u - 7u --> 450
5u --> 450
1u --> 90

a)

2u --> 2*90 = 180

the number of apples that David had at first = 180

b)

7u --> 7*90 = 630

630/2 = 315

the number of apples that David gave away = 315

[tracywham]

Thank you for your answer. I du\on’t quite understand. Where does the 2u and 12u comes from Siti?

[jieheng]

tracywham:

Thank you for your answer. I du\\on't quite understand. Where does the 2u and 12u comes from Siti?

Method 1

Siti had 6 times as many apples as David at first

If we assume D --> 1u , then S --> 6u , total (D+S) --> 7u

In the end , they had an equal number of apples

D --> 3.5u and S --> 3.5u after S gave 2.5u to D

2.5u --> 450
1u --> 180

For this method , you will have the decimal points , 3.5u and 2.5u .

Method 2

Siti had 6 times as many apples as David at first

I assume D --> 2u , then S --> 12u , total (D+S) --> 14u

In the end , they had an equal number of apples

D --> 7u and S --> 7u after S gave 5u to D

5u --> 450
1u --> 90

2u --> 2*90 = 180

For this method , you will have the whole numbers , 7u and 5u

[numeric]

tracywham:

hello, i need help on this question (with model drawing will be greatly appreciated):


Siti had 6 times as many apples as David at first. After Siti had given 450 apples to David, they had an equal number of apples.

a) Find the number of apples David have at first.

b) David gave away some apples and had half the number of apples
Siti had. How many apples did David give away?

http://i50.tinypic.com/doawr4.jpg\">

[mother777]

jieheng:

tracywham:

Thank you for your answer. I du\\on't quite understand. Where does the 2u and 12u comes from Siti?

Method 1

Siti had 6 times as many apples as David at first

If we assume D --> 1u , then S --> 6u , total (D+S) --> 7u

In the end , they had an equal number of apples

D --> 3.5u and S --> 3.5u after S gave 2.5u to D

2.5u --> 450
1u --> 180

For this method , you will have the decimal points , 3.5u and 2.5u .

Method 2

Siti had 6 times as many apples as David at first

I assume D --> 2u , then S --> 12u , total (D+S) --> 14u

In the end , they had an equal number of apples

D --> 7u and S --> 7u after S gave 5u to D

5u --> 450
1u --> 90

2u --> 2*90 = 180

For this method , you will have the whole numbers , 7u and 5u

Hi,
my DD is in P3 this year and I wonder if kids will be taught in which situation we need to assume 1u or 2u in such questions?

If you have any idea pls help to advise because I am not sure Kids will be taught to handle division with decimal numbers in P3.

[jieheng]

mother777:

jieheng:

[quote=\"tracywham\"]Thank you for your answer. I du\\on't quite understand. Where does the 2u and 12u comes from Siti?

Method 1

Siti had 6 times as many apples as David at first

If we assume D --> 1u , then S --> 6u , total (D+S) --> 7u

In the end , they had an equal number of apples

D --> 3.5u and S --> 3.5u after S gave 2.5u to D

2.5u --> 450
1u --> 180

For this method , you will have the decimal points , 3.5u and 2.5u .

Method 2

Siti had 6 times as many apples as David at first

I assume D --> 2u , then S --> 12u , total (D+S) --> 14u

In the end , they had an equal number of apples

D --> 7u and S --> 7u after S gave 5u to D

5u --> 450
1u --> 90

2u --> 2*90 = 180

For this method , you will have the whole numbers , 7u and 5u

Hi,
my DD is in P3 this year and I wonder if kids will be taught in which situation we need to assume 1u or 2u in such questions?

If you have any idea pls help to advise because I am not sure Kids will be taught to handle division with decimal numbers in P3.[/quote]Hi ,

If the question is
A had 6 times as many apples as B at first ................In the end , they had an equal number of apples.

It is better to make assumptions for A and B that their total no to be multiples of 2 .

First , assume B as 1u , then A --> 6u but their total no will be 7u which is not the multiples of 2.

Next , assume B as 2u , then A --> 12u and their total no will be 14u which is the multiples of 2.

[mother777]

Hi JieHeng,

Ok I understand the concept now.
thanks for the clear explanation

[angel]

Hi, I need help in solving this problem sum.


Elson has less than 40 sweets in a box.
When he ties the sweets in packets of 6, he has 2 sweets left.
When he ties them in packets of 8, he is short of 2 sweets.
How many sweets does he have in the box?

Thank you.

[mother777]

Multiples of 6: 6,12,18,24,36

Add 2. : 8,14,20,26,38

Multiples of 8: 8,16,24,32,40
Minus 2. : 6,14,22,30,38

Is it answer could be 14 or 38?