Q&A - PSLE Math

[MathIzzzFun]

Andrew Lee:

Hi


please clean up the pic.. difficult to figure out where are the x,y, z... if these are lying on the same straight line then there is no definite answer for x,y,z (y+z=180)... because the line DEF is not anchored.

cheers.

So sorry. I already clean up the pic, hope you can see it

http://i56.tinypic.com/hvdro2.jpg\">[/quote]

Hi

there is no definite solution because the line DEF is not anchored - x can take any value from 0 to 108 and y+z = 180.

cheers.

[MathIzzzFun]

Andrew Lee:

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Hi

please check question ...

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It is \"a\"..but then how to get (a) answer?
Hi

the question is flawed.

cheers.[/quote]

Can explain why which part of this question is flawed? [/quote]

hi

the angle DGH is 180 deg, so DGH is a straight line !! and not angled as shown.

cheers.

[looking4Tutor]

I have a long list of questions :oops: -


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TIA

[tianzhu]

looking4Tutor:

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Hi

Observe the pattern.

1*3
2*4
3*5

The sequence is formed by multiplying the figure number with (figure number +2)

n* (n+2)

(a) 7*9 ----- 63

(b) 80*(80+2) ----- 6560

(c) This one a bit tricky for PSLE kids, never mind about learning to solve the equation. Think logically and use GC.

With calculators, actually not too tedious.4355 is less than 6560, so figure number must be less than 80.

Try 70, wrong.Try 65, bingo that’s correct

65(65+2) -----4355

The answer is figure 65.

Best wishes

[tianzhu]

looking4Tutor:

http://i51.tinypic.com/2wrhumo.jpg\">

Hi

1/6 of the figure is shaded.

1 unit is shaded; this means 2.5 units are distributed to the unshaded area of a triangle.

Avoid decimals; multiply 2.5 by 2 to get 5.We must also multiply 1 unit by 2.

So shaded area is now 2 units and unshaded area of 1 triangle is 5 units.

Fraction of a triangle is shaded ----- 2/7.

Best wishes

[tianzhu]

looking4Tutor:

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Hi

The radius of the biggest circle is 4 times the radius of the shaded circle.

Assume 1 units for shaded circle as radius, its area is pi*1 -----1pi

Hence radius of biggest circle ------ Pi*4*4 -----16pi

Area of 3 shaded smallest circle ----- 3pi

Fraction of bigger circle shaded ----- 3pi/16pi ------- 3/16.

Best wishes

[tianzhu]

looking4Tutor:

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Hi

A is bigger than B
So obviously the difference in area is (A-B)

As in any questions on composite figures, look for familiar shapes.

Area of rectangle – B + area of small quadrant (r5) + A -------- area of big quadrant.

A-B -------- area of big quadrant – small quadrant – the area of rectangle

Area of big quadrant ------ (3.14*100)/4 ------- 78.5

Area of small quadrant ------ 19.625

Area of rectangle ----- 5*10 -------50

A-B ------ 78.5 – 19.625 -50 ------- 8.875

Best wishes

[tianzhu]

looking4Tutor:

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Hi

You may work in percentage or convert into units. It’ll be helpful to draw a MD if you need one.

Ace ----- 120 units
Bert -----100 units

Ace gave 12 units and Bert gave 10 units to Cain.

When Cain received 22 units from A and B, his share increased by 40%.

40% --- 22units
100% ---- 55 units

Hence his original units is 55 and in the end he had (55+22) or 77 units

Ace had 108 units in the end.(120-12)

108 - 77 ------ 31

31 units ----- 62
1 unit -----2

At first, Bert had (100*2) or 200 books.

Best wishes

[Fairy Best Freinds]

Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil, find the cost of a pencil.


Thank you.

[Fairy Best Freinds]

At first, Ravi had $22 more than Vincent. He gave 40% of his money to Vincent. Vincent then gave 25% of his money to Ravi. In the end, Vincent had $68 more than Ravi. How much did Vincent give Ravi?


Thank you.