Q&A - PSLE Math

[tianzhu]

looking4Tutor:

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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.

[tianzhu]

looking4Tutor:

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Hi

360 degrees ------ 5400
1 degree ------ 15

Shopping + airfare -----360 –(160+90) -----110
Airfare ----- 60%
Shopping ------ 50%

Amount spent on hotel and meals ------ 250 degrees ------- 3750

Amount spent on shopping ------ 50 degrees ------- 750

Best wishes

[MathIzzzFun]

looking4Tutor:

I have a long list of questions :oops: -


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TIA

Hi

alternate approach ..

Figure 1 = 3 = 2 x 2 -1 = (1+1)^2 -1
Figure 2 = 8 = 3 x 3 -1 = (2+1)^2 -1
Figure 3 = 15 = 4 x 4 -1 = (3+1)^2 -1

Figure N = (N+1)^2 -1 = C (number of circles)
N= sqrt(C+1) -1

a) Figure 7 = (7+1)^2 -1 = 63
b) Figure 80 = (80+1)^2 - 1= 6560
c) Number of circles = 4355, sqrt(4355+1)-1 = 65
Figure 65 has 4355 circles.

cheers.

[tianzhu]

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.

Hi

You may use MD for this question.

Sorry no time to draw now, but there are some examples in previous posts.

NB ----- 12
Pencils ----- 9.6

9.6/4 ------ 2.4

12 – 2.4 ----- 9.6

A notebook costs $3.20 more than a pencil.
9.6/3.2 ----- 3

There are 3 NB, therefore 12 pencils.

Cost per pencil ----- 9.6/12 ------ 80 cents.

Best wishes

[tianzhu]

looking4Tutor:

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Hi

For 6 minutes, water filled by Tap A and Tap B ------ (10.2+4.5) *6 ------- 88.2

Tap B turned off and Tap C turned on

Difference in flow rate between Tap A and Tap C ------ 10.2 – 3.5 ---- 6.7

322.7 – 88.2 ------ 234.5

234.5/6.7 ------- 35

Best wishes