Q&A - P2 Math

[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.

[Taurus]

Anyone can confirm answer is 76 and not 67 as in answer sheet :

Qns : i am a two digit number. The difference between my tens digit and ones digit is 1. My digits add up to 13. What number am I?

[mother777]

Hi Tauras,


The answer could be both 76 and 67.

Since the question states: the difference between my tens digit and ones digit is 1, it does not matter in which place the \"7\" is.

If the question mentioned, \"When we subtract the number in ones digit from the number in tens digit, the answer is 1\" --> then the answer will definitely be 76.

just my opinion on this..

[Taurus]

mother777:

Hi Tauras,


The answer could be both 76 and 67.

Since the question states: the difference between my tens digit and ones digit is 1, it does not matter in which place the \"7\" is.

If the question mentioned, \"When we subtract the number in ones digit from the number in tens digit, the answer is 1\" --> then the answer will definitely be 76.

just my opinion on this..

Thanks, think will ask my son to chk with teacher..

[fohope]

chamonix:

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

Hi Chamonix,
I do not know the answer and had sent email to check with the teacher.
No reply from her yet.
My answer is the same as you.
Thanks for your reply.