Q&A - P2 Math

[Sun_2010]

5 girls and 3 boys in each group

[fohope]

Sun_2010:

5 girls and 3 boys in each group

Thanks Sun 2010

[Kitty75]

Hi, pls help me to solve this question.


Mrs Hoe had a total of twenty $10-notes and $5-notes. The total value of all the notes was $120. How many $10-notes did she have?

[BigDevil]

Kitty75:

Hi, pls help me to solve this question.


Mrs Hoe had a total of twenty $10-notes and $5-notes. The total value of all the notes was $120. How many $10-notes did she have?

I know DD was taught to create a table like this:
http://i52.tinypic.com/24xeubs.jpg\">

But is there other way?

[fohope]

Hi

Could anyone help to solve this? Thanks.
Find the missing number
16 - 8 - 12 - 6 - 10 - ? - 9

[BlurBee]

BigDevil:

Kitty75:

Hi, pls help me to solve this question.


Mrs Hoe had a total of twenty $10-notes and $5-notes. The total value of all the notes was $120. How many $10-notes did she have?

I know DD was taught to create a table like this:

But is there other way?

:hi5:
My DD also use this method.

[metz]

KELLY2009:

Hi

Could anyone help to solve this? Thanks.
Find the missing number
16 - 8 - 12 - 6 - 10 - ? - 9

Is the answer 5?

divide by 2, then add 4.

16/2 = 8
8+4 = 12
12/2 = 6
6 + 4 = 10
10/2 =5
5 + 4 = 9

[allcc6]

BigDevil:

Kitty75:

Hi, pls help me to solve this question.


Mrs Hoe had a total of twenty $10-notes and $5-notes. The total value of all the notes was $120. How many $10-notes did she have?

I know DD was taught to create a table like this:
http://i52.tinypic.com/24xeubs.jpg\">

But is there other way?

Can use heuristic method (think it's called assumption method) :

Assuming all are $5-notes,
20 x $5 = $100

Balance is $120 - 100 = $20

(hence this extra $20 must be from the remaining $5 of the $10-notes)

$20 / 5 = 4

Therefore, there are 4 $10-notes.

[BigDevil]

Thanks, allcc6!


That’s a neat way to solve the problem.
But I foresee I need to do some major explanation to DD.

[teachingmum]

Hi Big Devil,


You may like to draw or use pictoral aids to show your child.

First, draw or cut out 20 rectangles (rep $5).
Next, ask your child to find the total value, which is $100.
Lead her to see there is still an excess of $20 and ask her why. (Not all are $5, some are $10 and so, for some rectangles, we must add another $5 * the difference*)
Give her another 4 $5 (total $20) and ask her to add to some of the $5.
In the end, she should see that there are 4 $10.

Try similar method for one or two more questions. Once she understands this method, can do without pictoral aids/ manipulatives and just use the method.