Tutor MathsGuru: Ask me for your burning Maths questions!

[tianzhu]

Hi YLH88


If you prefer to do it by tabulated form, here is the alternative.For this question, I'd suggest MD.

http://farm3.static.flickr.com/2706/4364057007_f2862089a8_o.jpg\">

Best wishes

[YLH88]

Hi Tianzhu & BigDevil,


Thank you very much! Trying to digest the solution.

But I still don't understand, when I compare the solution with the Jim and Ken question, the initial unit and part did not include the number that was eaten for the Jim and Ken question but here it is included. When do I have to include and when do I not include ??
:?


http://www.postimage.org/image.php?v=gxCLBWJ

[tianzhu]

YLH88:

But I still don't understand, when I compare the solution with the Jim and Ken question, the initial unit and part did not include the number that was eaten for the Jim and Ken question but here it is included. When do I have to include and when do I not include ??
[/url]

Q1) Jim bought some chocolates and gave half of it to Ken. Ken bought some sweets and gave half of it to Jim. Jim ate 12 sweets and Ken ate 18 chocolates. The ratio of Jim's sweets to chocolates became 1 : 7 and the ratio of Ken's sweets to chocolates Ken became 1:4.How many sweets did Ken buy?

Q2) Jack had some watermelons. He gave half of his watermelons to Terry. Terry then gave half of his durians to Jack. Jack sold 212 watermelons and Terry sold 56 durians. In the end, the ratio of watermelons to durians for Jack and Terry is 1:8 and 1:2 respectively. How many watermelons did Jack have at first?

Hi

Put these two questions side by side and compare the differences.
Look pretty much similar, but take note of the subtle differences.

In the first question, Jim ate the sweets given by Ken. For the second question, Jack sold his remaining half of his water melon.

Best wishes

[Dharma]

YLH88:

Hi Tianzhu & BigDevil,


Thank you very much! Trying to digest the solution.

But I still don't understand, when I compare the solution with the Jim and Ken question, the initial unit and part did not include the number that was eaten for the Jim and Ken question but here it is included. When do I have to include and when do I not include ??
:?


http://www.postimage.org/image.php?v=gxCLBWJ

Hi YLH88,

Modified the Jim & Ken to this qn.



http://www.postimage.org/image.php?v=gxCNy9J

[YLH88]

Hi Dharma,


Thank you very much!

[rubydoll]

Good morning.


Kindly help on the following maths sums:

1) The lengths of two rectangles are 11m and 19m respectively. Their total area is 321meter square. What is the diferrence in their areas?

2)Mrs Tan had $800 at first. 80% of her money consisted of $5 notes and the rest were $10 notes. After she spend some $5 notes, the remaining $5 notes was 60% of the money she had left. How much did Mrs Tan spend?

3)There are 147 pages in a science textbook. What is the total number of digits on all the pages of the textbook.

4)A group of people went hunting. On the average, 6 people hunted 5 rabbits, 15 people hunted 2 deer and 10 people hunted 1 buffalo. The total number of animals hunted was 6 more than the total number of people who went hunting. How many people went hunting?

Many thanks for your help
rubydoll

[Dharma]

rubydoll:

Good morning.


Kindly help on the following maths sums:

1) The lengths of two rectangles are 11m and 19m respectively. Their total area is 321meter square. What is the diferrence in their areas?

2)Mrs Tan had $800 at first. 80% of her money consisted of $5 notes and the rest were $10 notes. After she spend some $5 notes, the remaining $5 notes was 60% of the money she had left. How much did Mrs Tan spend?

3)There are 147 pages in a science textbook. What is the total number of digits on all the pages of the textbook.

4)A group of people went hunting. On the average, 6 people hunted 5 rabbits, 15 people hunted 2 deer and 10 people hunted 1 buffalo. The total number of animals hunted was 6 more than the total number of people who went hunting. How many people went hunting?

Many thanks for your help
rubydoll

Hi rubydoll,

Q4 does not seem like PSLE kind of Qn. Do u know the answer?

1)\tThe lengths of two rectangles are 11m and 19m respectively. Their total area is 321meter square. What is the difference in their areas?

There are 2 unknowns with 1 equation…. Need to solve by trial and error.
11 x W1 + 19 x W2 = 321
11W1 + 19W2 = 321

W1 = 5 & W2 = 14 (trial & error)

Difference in area = (19x14) – (11x5) = 211m2

2)\tMrs Tan had $800 at first. 80% of her money consisted of $5 notes and the rest were $10 notes. After she spent some $5 notes, the remaining $5 notes was 60% of the money she had left. How much did Mrs Tan spend?

80% of money - $640 ($5 notes)
20% of money - $160 ($10 notes)

After spending some $5 notes, the remaining $10 notes were 40% of money left.

40% - $160
20% - $80
60% - $240

Amt of money spent = $640 - $240 = $400

3)There are 147 pages in a science textbook. What is the total number of digits on all the pages of the textbook.

Pages 1 ~ 9 ….. 9 digits
Pages 10 ~ 99 … (99-10+1)x 2 = 180 digits
Pages 100 ~ 147 … (147 – 100 + 1) x 3 = 144 digits

Total no. of digits = 9 + 180 + 144 = 333

4) A group of people went hunting. On the average, 6 people hunted 5 rabbits, 15 people hunted 2 deer and 10 people hunted 1 buffalo. The total number of animals hunted was 6 more than the total number of people who went hunting. How many people went hunting?

On an average;
6 people hunted 5 rabbits; 1 person hunted 5/6 rabbit (sound ridiculous)
15 people hunted 2 deers; 1 person hunted 2/15 deer
10 people hunted 1 buffalo; 1 person hunted 1/10 buffalo

Therefore, we can say that 1 person can hunt 5/6 of a rabbit , 2/15 of a deer, 1/10 of a buffalo (or a combination of all three)

30 persons can therefore hunt 25 rabbits, 4 deers & 3 buffaloes (Total = 32 animals)
There are 2 more number of animals hunted compared to the number of hunters (32 – 30 = 2)

Therefore; in order to have 6 more number of animals hunted compared to the number of hunters; there must be (30 x 3 = 90 hunters)

96 animals – 90 hunters = 6

[fudgemum]

Dharma:

1)\tThe lengths of two rectangles are 11m and 19m respectively. Their total area is 321meter square. What is the difference in their areas?

There are 2 unknowns with 1 equation…. Need to solve by trial and error.
11 x W1 + 19 x W2 = 321
11W1 + 19W2 = 321

W1 = 5 & W2 = 14 (trial & error)

Difference in area = (19x14) – (11x5) = 211m2

Hi Dharma,

If I do remember correctly these questions are from Rulang Primary CA1 2009 test paper. Technically there is one more answer to the above question.
24*11 +3*19 = 321
24*11 - 3*19 = 207.
But in this case the breadth (24) is bigger than the length (11).

[Dharma]

fudgemum:

1)\tThe lengths of two rectangles are 11m and 19m respectively. Their total area is 321meter square. What is the difference in their areas?

There are 2 unknowns with 1 equation…. Need to solve by trial and error.
11 x W1 + 19 x W2 = 321
11W1 + 19W2 = 321

W1 = 5 & W2 = 14 (trial & error)

Difference in area = (19x14) – (11x5) = 211m2

Thanks fudgemum. Strange that a qn can be set with more than 1 answer.

[fudgemum]

Hi,


I am not able to draw the picture.There are three identical circles A, B and C. The circumference of each circle passes through the centre of the other two circles. So we have regions like
A only, B only, C only,
A and B only, B and C only, A and C only,
A and B and C (center portion).

How do you proove that
A and B only, B and C only, A and C only (i.e A insersection B, B intersection C , and C intersection A)
this area is half of the circle.
TIA