Q&A - PSLE Math

[portal]

small:

portal:

3)I have this question to ask as well.An empty retangular tank 0.5 meters long and 0.4 meters wide is filled with water from 2 taps,Tap A and Tap B.Tap A

was turned on and it fills the tank with water at a rate of 9 litres per minute.Tap B was turned on and it fills the tank with water at a rate of 11 litres per minute.What is the height of the water in the tank after Tap B was turned on for 10 minutes? leave your answer in meters. :imdrowning:

Hi,

Let me try to solve.

Base of the rectangular tank ----- 0.5m x 0.4m = 0.2 m square

I presumed Tap A and Tap B were turned on together
Every 1 minute ----- 11 + 9 = 20 litres
after 10 minutes ----- 20 x 10 = 200 litres = 0.2 m cube (1000 litres =1 m cube)

Height of tank x 0.2 m square =0.2 m cube
Height of tank = 1 m

In a exam will i get correct if i write 1m or 1.09m :?

[tianzhu]

danishcookies:

Good day, I have 2 math Ques.

1) In a school choir, the ratio of the number of boys to the number of girls in is 2:3, 1/4 of the boys and 1/2 of the girls wear spectacles.If there are 48 pupils who wear spectacles. How many pupils are there in the choir?

2)John has $28 more than Peter. 1/3 of John's money is equal to 4/5 of Peter's money. Find John's money.

Hi

Q1

Boys: Girls ------- 2:3 -------4:6

¼ of boys --------1u
½ of girls --------- 3u

1u+3u ----- 4u -------48
1u ------ 12
\t
10u ----- 12*10 ------ 120

Q2

1/3 of John's money ------ 4/5 of Peter's money.

Make the numerator the same.

4/12 of John's money ------ 4/5 of Peter's money.

John ------ 12 units
Peter ----- 5 units

7 units ------ 28
1 unit ----- 4

John ----- 12*4 ------48

Best wishes

[tianzhu]

isetan:

hi tianzhu,


for question two, is the answer 11:9?

Hi

Yes, you're correct.

Best wishes

[Superbugs]

Nan Hua CA1 P6 2011

Q7:
I have some red and blue ribbons in a bottle.
If I add in 20 red ribbons, 60% of my ribbons are blue.
If I add in another 60 blur ribbons, 75% of my ribbons are blue.
How many ribbons have I in the bottle?
Please help with this question. Tks

[Superbugs]

Man Hua CA1 P6 2011

Q11.
Rectangle A overlaps with Rectangle B. Rectangle A is twice the size of Rectangle B. If 1/3 of Rectangle B overlaps with Rectangle A, what fraction of Rectangle A overlaps with Rectangle B?

[Superbugs]

Superbugs:

Man Hua CA1 P6 2011

Q11.
Rectangle A overlaps with Rectangle B. Rectangle A is twice the size of Rectangle B. If 1/3 of Rectangle B overlaps with Rectangle A, what fraction of Rectangle A overlaps with Rectangle B?

Actually this is very easy. I got the answer as 1/6. Tks

[Superbugs]

Nan Hua CA1 P6 2011

Q15
A farm has some ducks and cows.
The ratio of the number of animals to the total number of legs is 8:23.
Express the number of ducks as a fraction of the cows.
Give your answer in the simplest form.
Pls assist with this question. Tks

[peggy]

Please help !


The ratio of the amount of money in jane’s account to the amount of money in May’s account was 11:7. Jane and May shared the cost of a computer in the ratio of 3:1. Jane used 1/2 of her money to pay for her share of the computer. May had $620 left after paying for her share. What was the cost of the computer?

Thanks!

[Superbugs]

Nan Hua CA1 P6 2011

Q14.
My salary is 1/5 more than my sister but 20% less than my brother. If our total salary is $11,100, what is my sister’s salary?

If Me=100%
Brother =120%
Sister=80%
80/300x11,100=2960
but answer is $3000?
Pls assist. Tks

[mathfreak]

Superbugs:

Nan Hua CA1 P6 2011

Q7:
I have some red and blue ribbons in a bottle.
If I add in 20 red ribbons, 60% of my ribbons are blue.
If I add in another 60 blur ribbons, 75% of my ribbons are blue.
How many ribbons have I in the bottle?
Please help with this question. Tks

Not sure about using model method for this one but here is how I solved this type of question when I was in primary school:
Let x be the number of red ribbons and y be the number of blue ribbons.
Then: (x+20)/y = 40/60 = 2/3
and x/(y+60) = 25/75 = 1/3
Solving the simultaneous equations for x and y we get:
2y = 3x + 60, and 3x = y + 60
Hence y = 60 + 60 = 120.
x = 60.
x+y = 120 + 60 = 180.
Ans: 180 ribbons.