Q&A - PSLE Math

[ck123]

Hi smileplease


It is 840/2800 X 100

[MathIzzzFun]

smileplease:

Anyone knows how to do this Q :


There were 1960 workers in a garment factory this year. This is 840 less than that of last year. Find the percentage decrease in the number of workers?

How do we determine it is 840/2800 x 100 OR 840/1960 x 100?

thanks.

Hi

the question is asking for percentage decrease which means that the reference point is last year.

Number of workers last year = 1960 + 840 = 2800

so, percentage decrease = 840/2800 x 100%

cheers.

[smileplease]

atutor2001:

smileplease:

Anyone knows how to do this Q :


There were 1960 workers in a garment factory this year. This is 840 less than that of last year. Find the percentage decrease in the number of workers?

How do we determine it is 840/2800 x 100 OR 840/1960 x 100?

thanks.

This one I know.
Decrease is changing from BIG to small so the original/start is BIG -> divide by BIG
Increase is changing from SMALL to big so the original/start is SMALL -> divide by SMALL
That was how I told my kids in those good old days.

:thankyou:

[smileplease]

Need help on this Q:


Ginny had two boxes of greeting cards. After she had transferred 1/5 of the greeting cards in box A to box B, the ratio of the number of greeting cards in box A to the number of greeting cards in box B is 3:5. What was the ratio of the number of greeting cards in box A to the number of greeting cards in box B at first?

[MathIzzzFun]

smileplease:

Need help on this Q:


Ginny had two boxes of greeting cards. After she had transferred 1/5 of the greeting cards in box A to box B, the ratio of the number of greeting cards in box A to the number of greeting cards in box B is 3:5. What was the ratio of the number of greeting cards in box A to the number of greeting cards in box B at first?

Hi

after transfer, Box A : Box B = 3 : 5 = 12u : 20u
Before transfer, Box A = 5/4 x 12u = 15u

Before transfer, Box A : Box B = 15u : 20u-3u = 15: 17

cheers.

[MathIzzzFun]

Angel25:

Pls HELP!!



Roy jogged from his house to the playground and back at 10km/h. He reached home at 12.18pm. If he jogged at 3km/h slower, he would reach home at 1.30pm. If he wanted to reach home at 12.45pm to have his lunch, at what speed did he have to jog?

Thanks!!

Hi

speed ratio, initial : slower = 10 : 7
time ratio, initial : slower = 7: 10

1330-1218 = 72min = 1 1/5h
so 3u = 1.2h, 7u = 1.2/3 x7 = 2.8h = 2h 48min

To reach home at 12.45pm, means to take 1245-1218 = 27min more, ie total time to jog at new speed = 2h 48 min + 27min = 3h 15 min = 3.25h

new speed = 2.8/3.25 x 10 km/h= 112/13 km/h = 8 8/13 km/h

cheers.

[pensiveowl]

Pls help with this question thanks:


Mr Ho and Mrs Lee took part in a chess competition. Mr Ho played against 1/3 as many men as women. Mrs Lee played against 2/5 as many men as women. How many women took part in the chess competition?

[pensiveowl]

Could someone pls help with this one as well - thanks


The ratio of the number of green marbles to the red marbles in a box is 6 : 5. After 60 green marbles and 60 red marbles were removed from the box. the ratio of the number of green marbles to red marbles became 9 : 7. How many red marbles were there in the box at first?

[tianzhu]

Hi


CHS P6 Prelim Q16 2010

I’ve attempted to breakdown the question into familiar shapes which students are familiar with.

PLSE students should be very comfortable with familiar shapes such as triangle, circles, and squares. They should also be able to find out the area of the eye or leaf or rugby ball.

I’ll leave it to you to work out the detailed calculations as students may have their preferred way of working out the circumferences and areas of shapes. For example some students may prefer to calculate the area of the triangle while others may want to find out the areas of two small squares (10).

Hope this helps.

Best wishes.

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[tianzhu]

pensiveowl:

Could someone pls help with this one as well - thanks


The ratio of the number of green marbles to the red marbles in a box is 6 : 5. After 60 green marbles and 60 red marbles were removed from the box. the ratio of the number of green marbles to red marbles became 9 : 7. How many red marbles were there in the box at first?

Hi

The number of green marbles and red marbles removed from the box are the same.

Hence the difference between the number of green marbles and red marbles stay the same before and after.

At first.
Green: Red ------ 6:5 -------12:10
Difference ----- 1 ------ 2

In the end
Green: Red ------ 9:7
Difference ----- 2

Make the difference the same.

3 units ------ 60
1 unit ------ 20

At first, red marbles -------10*20 -------200

Best wishes