Q&A - PSLE Math

[alfretztay]

We have two ratios here, but they are ratios of two different numbers. This is the units and parts pattern, and this is the way I'll do it. It's not the only way.

We use units for Jane and parts for Dinah.

Jane (from 25%) 1u : 3u
Dinah (from 50%) 1p : 1p

The total number of red and blue beads doesn't change.

Red beads: 3u + 1p = 610
Blue beads: 1u + 1p = 390

[p]
[----610----]

[p]
[390]

[p] is common to top and bottom, and it adds up to 390. The top becomes


[220]

which means u = 110. Jane has 4u altogether so this is 440 beads.

a. Jane has 440 beads in the end.

Now for part b.

Dinah has p blue beads in the end
[p] is 390, and u is 110, which makes p 390 - 110 = 280
She started with 220 beads, so she received 280 - 220 = 60 beads from Jane.

b. Dinah received 60 beads from Jane.

MathWithModels

! would solve the above problem as follows :

Before

J -> 210(blue) + 390(red)

D -> 180(blue) + 220(red)

After

J -> 1u(blue) + 3u(red) = 4u(total)

D -> 1p(blue) + 1p(red)

(a) 1u + 1p -> 390

3u + 1p -> 610

2u -> 220

1u -> 110

4u -> 440

(b) 1p -> 280

280 – 180 = 100

Ans : (a) 440 beads and (b) 100 blue beads.

[alfretztay]

(a) Let the number of cookies in each small packet be 1u.
5/7 -> 14 small packets(14u) + 4 boxes(16u) = 30u
1/7 -> 6u
1 – 5/7 = 2/7
2/7 x 1/4 = 1/14

(b) 2/7 -> 12u
3/4 x 12u = 9u(6 big packets) = 6u + 36
[12u – 9u = 3u(given away)]
3u -> 36
1u -> 12
12 + 6 = 18
Ans : (a) 1/14; (b) 18 cookies.

[MathWithModels]

Yes, sorry. I was careless in part b. Thanks for the correction, alfretztay!

MathWithModels.

[Daddy]

Thank you very much all of the helpful people...

[Jerico]

Please help with the attached algebra question :-



Thank you in advance !

[Jerico]

Kindly help. Thank you very much !

[tanxexy]

Please help with the attached algebra question :-



Thank you in advance !

(a) From the diagram, the volume of the liquid is 800 cm3.
Volume = Area of Base * Height
=> Area of Base = 800/x

(b) If x = 8, Area of Square Base = 100 cm2
=> Length of Base = Sqrt(100) = 10 cm

[tanxexy]

Kindly help. Thank you very much !

[alfretztay]

Please help with the attached algebra question :-



Thank you in advance !

(a) From the diagram, the volume of the liquid is 800 cm3.
Volume = Area of Base * Height
=> Area of Base = 800/x sq cm

(b) If x = 8, Area of Square Base = 100 cm2
=> Length of Base = Sqrt(100) = 10 cm

[alfretztay]

Kindly help. Thank you very much !

I would solve the question as follows :

(a) Area of the square = 2(1/2 times 2x times x) = 2(x^2) sq cm.

(b) Area of shaded segments = (pi time x time x) – 2(x^2) = (pi – 2)x^2 sq cm.