## Q&A - PSLE Math

### Re: Q&A - PSLE Math

Shaded Area = Area of Big Circle + Area of Small Circle - Area of Triangle.hoddle wrote:Hi

Please solve the below. Thks.

See post below, for explanation,

http://www.kiasuparents.com/kiasu/forum ... 9#p1498999

Also look into http://mathseason.com/skills/area.html

Number 6 of the teaching teaches method to find the shaded areas of such questions.

### Re: Q&A - PSLE Math

Please help

Alda's age is now thrice that of Rena's age some years ago,Rena age now is the same as Aldas age some years ago. If the sum of their ages now is 30 years ,

How old is Alda now?

In how many years time will Rena's age be 80% of Aldas age?

Alda's age is now thrice that of Rena's age some years ago,Rena age now is the same as Aldas age some years ago. If the sum of their ages now is 30 years ,

How old is Alda now?

In how many years time will Rena's age be 80% of Aldas age?

### Re: Q&A - PSLE Math

To get from lobby to level 1 ,Luther has to climb 2 identical flights of stairs. For the first flight of stairs ,Luther walked up some steps and ran up 10 steps,and took a total of 100 seconds. For the second flight of stairs ,he ran up 19 steps and walked up the rest of the steps ,and took a total of 19 seconds. How long would Luther take to walk up both flights of stairs? Leave your answer in seconds.

### Re: Q&A - PSLE Math

COOKIE64 wrote:Please help

Alda's age is now thrice that of Rena's age some years ago,Rena age now is the same as Aldas age some years ago. If the sum of their ages now is 30 years ,

How old is Alda now?

In how many years time will Rena's age be 80% of Aldas age?

Code: Select all

```
Some year ago be 's' Now
Rena's age be u u+s
Alda's age is (u+s) 3u
```

4u+s =30 --(1)

u+u+s = 30-2s

2u+s = 30-2s

2u+3s =30

4u+6s=60 ---(2)

(2) - (1)

5s=30

s=6

4u+6=30

u=6

a)Alda now is 3u = 18 years old

b)Rena now is u+s = 12 years old

(12 + Y)/(18+y) = 0.8

12+y = 14.4 + 0.8y

0.2y = 2.4

y= 12 year

### Re: Q&A - PSLE Math

Running steps,COOKIE64 wrote:To get from lobby to level 1 ,Luther has to climb 2 identical flights of stairs. For the first flight of stairs ,Luther walked up some steps and ran up 10 steps,and took a total of 100 seconds. For the second flight of stairs ,he ran up 19 steps and walked up the rest of the steps ,and took a total of 19 seconds. How long would Luther take to walk up both flights of stairs? Leave your answer in seconds.

19 steps => 19sec

10 steps => 100secs , -> Each reducing steps increase by 9 sec

1 step -> 181 sec

0 step -> 190sec, => 100% walking, no running at all.

Two flight of steps = 2X190 = 380secs.

### Re: Q&A - PSLE Math

An easier way.COOKIE64 wrote:Please help

Alda's age is now thrice that of Rena's age some years ago,Rena age now is the same as Aldas age some years ago. If the sum of their ages now is 30 years ,

How old is Alda now?

In how many years time will Rena's age be 80% of Aldas age?

p= present

S= some years ago

A(P): R(S) : Total

3 : 1 : 4

R(P) : A(S) : Total

1 : 1 : 2

*2

2 : 2 : 4

5u - 30

1u - 6

6 x 3 =

**18**

Code: Select all

```
A:R Difference.
3:2 1
A:R
5:4 1
```

**12 years**

- alfretztay
- KiasuGrandMaster
**Posts:**1199**Joined:**Sun Sep 12,**Total Likes:**5

### Re: Q&A - PSLE Math

For Dave :bhfg0302 wrote:Help

50c : 2u - 1u = 1u

$1 : 1p - 16

1u x 2 = 2u -------- 1p - 16

For Wayne :

50c : + 1u - 10

$1 : 2p - 1p = 1p

(1u - 10) x 5 = 5u - 50 -------- 1p

2u ------- (5u - 50) - 16

3u ------- 66

1u ------- 66/3 = 22

2u ------- 22 x 2 = 44

44 x 0.5 = 22

Ans : $22.

### Re: Q&A - PSLE Math

Gary bought some candies and gave 2/3 of its to Russell. Russell bought some toffees and gave 2/3 of its to Garry. Gary ate 6 toffees and Russell ate 6 candies . The ratio of Gary's toffees to candies become 2:1 and the ratio of Russell's toffees to candies is 4:5 how many toffees did Russell buy?

My solution.

Gary

T:C

2T:1C -6

2u:1u

Russell

T:C

1T:2C

-6

4u:5u

1c-> 1u+6

2c-> 2u+12

5u=2u+12

3u=12

1u=4

4u=16(T)

16X3=48

Can it be solved this way or is it a fluke?

My solution.

Gary

T:C

2T:1C -6

2u:1u

Russell

T:C

1T:2C

-6

4u:5u

1c-> 1u+6

2c-> 2u+12

5u=2u+12

3u=12

1u=4

4u=16(T)

16X3=48

Can it be solved this way or is it a fluke?