Q&A - PSLE Math

[hoddle]

Hi

Please solve the below. Thks.

[Ender]

Hi

Please solve the below. Thks.

Shaded Area = Area of Big Circle + Area of Small Circle - Area of Triangle.

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.

[COOKIE64]

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?

[COOKIE64]

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.

[Ender]

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

3u+u+s = 30
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

[Ender]

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.

Running steps,
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.

[bhfg0302]

Help

[NerdyMath]

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?

An easier way.

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

2u - 6*2 = 12

12 years

[alfretztay]

Help

For Dave :
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.

[NerdyMath]

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?