Q&A - PSLE Math

[fxchow]

tianzhu:

fxchow:

But I do not understand this part:


Compare heights in B to A
1.5/2 ---- 3/4
why 1.5/2 not 1.5/3 (I thought vol of tank A is 3)

Hi, hope this helps.

http://farm4.static.flickr.com/3391/3649016855_c668bd5993_o.jpg\">

Hi Tianzhu,

Unable to view the photo :?

[Tang]

tianzhu:

fxchow:

But I do not understand this part:


Compare heights in B to A
1.5/2 ---- 3/4
why 1.5/2 not 1.5/3 (I thought vol of tank A is 3)

Hi, hope this helps.

http://farm3.static.flickr.com/2472/3649870386_00154e89da_o.jpg\">

Water level in Tank B is 3/4 that of Tank A after the transfer.

Water level in Tank B is 3/2 that of Tank A after the transfer.
Water level in Tank B is 3/4 its height.

[tianzhu]

Tang:

Water level in Tank B is 3/4 that of Tank A after the transfer.

Water level in Tank B is 3/2 that of Tank A after the transfer.
Water level in Tank B is 3/4 its height.

Hi
Thank you for the correction.Should be read as

Water level in Tank B is 3/4 the height of the tanks(since both tanks have the same heights)

[tweet]

Hi,


can pls help solve with this question with model diagram.TIA

There were 4 times as many apples as oranges in a box.If 60 additional apples and 9 more oranges were put into the box, the new number of apples will becomes 6 times the the new number of oranges in the box. How many apples were there in the box at first?

Thanks

[Tang]

tweet:

Hi,


can pls help solve with this question with model diagram.TIA

There were 4 times as many apples as oranges in a box.If 60 additional apples and 9 more oranges were put into the box, the new number of apples will becomes 6 times the the new number of oranges in the box. How many apples were there in the box at first?

Thanks

Before (model)
Apples -- 4 units
Oranges -- 1 unit

After (model)
Apples -- 6 Big units
Oranges -- 1 Big unit

Redraw
Oranges -- 1 unit + 9 [Divide the Big unit]
Apples -- 4 [1 unit + 9] + 2 [1 unit + 9]

2 units + 6 x 9 --> 60
2 units --> 60 - 54 = 6
1 unit --> 6 / 2 = 3

Apples: 4 units --> 4 x 3 = 12 at first.

[tweet]

Tang:

tweet:

Hi,


can pls help solve with this question with model diagram.TIA

There were 4 times as many apples as oranges in a box.If 60 additional apples and 9 more oranges were put into the box, the new number of apples will becomes 6 times the the new number of oranges in the box. How many apples were there in the box at first?

Thanks

Before (model)
Apples -- 4 units
Oranges -- 1 unit

After (model)
Apples -- 6 Big units
Oranges -- 1 Big unit

Redraw
Oranges -- 1 unit + 9 [Divide the Big unit]
Apples -- 4 [1 unit + 9] + 2 [1 unit + 9]

2 units + 6 x 9 --> 60
2 units --> 60 - 54 = 6
1 unit --> 6 / 2 = 3

Apples: 4 units --> 4 x 3 = 12 at first.

Hi Tang

The answer is 60 apples at first.

Thanks

[Tang]

tweet:

Tang:

[quote=\"tweet\"]Hi,


can pls help solve with this question with model diagram.TIA

There were 4 times as many apples as oranges in a box.If 60 additional apples and 9 more oranges were put into the box, the new number of apples will becomes 6 times the the new number of oranges in the box. How many apples were there in the box at first?

Thanks

Before (model)
Apples -- 4 units
Oranges -- 1 unit

After (model)
Apples -- 6 Big units
Oranges -- 1 Big unit

Redraw
Oranges -- 1 unit + 9 [Divide the Big unit]
Apples -- 4 [1 unit + 9] + 2 [1 unit + 9]

2 units + 6 x 9 --> 60
2 units --> 60 - 54 = 6
1 unit --> 6 / 2 = 3

Apples: 4 units --> 4 x 3 = 12 at first.

Hi Tang

The answer is 60 apples at first.

Thanks[/quote]Checks
4 units -- 12, 1 unit -- 3

12 + 60 = 72
3 + 9 = 12

72 / 12 = 6 times (correct)

So answer 12 apples at first is correct. [60 is added, not the original number.]

[tweet]

Hi Tang


Thanks a lot. Now i see the picture after you summarise.

[small]

Once again thanks for your time.


Question:

For every question Lilian answered correctly in a quiz, she scored 5 points. 2 points were deducted for each incorrect answer. For every 20 questions Lilian answered, 5 were wrong. She scored a total of 340 points in the quiz.

a) How many questions did Lilian answer altogether?
b) How many points less did she score because of the incorrect answer?

[tianzhu]

Hi

Hope this helps.

Other than Guess and Check, the other method which is more effective is to use Grouping.

For every 20 questions, 5 were wrong, meaning there were 15 correct ones.

Marks achieved are (15*5) – (5*2) --- 65
5 groups of 20 questions gave you (5*65) --- 325
(340-325) --- 15 marks for 3 correct answers.

a)Lilian answered (5*20) + 3 -----103 questions

b)Two ways to get the answer

Method 1
(103*5) – 340 --- 175 points

Method 2
For every wrong answer, she lost (5+2) points
Therefore, she scored (25*7) ---- 175 points less