Q&A - PSLE Math

[tianzhu]

jessielu:

Need help on below question:


A dictionary cost $11 more than a book.  The book cost $45 more than a magazine.  Mr lee paid a total of $252 for 6 pieces of each item.  What is the cost of a book?

Appreciate the steps to solve this

Hi

6 pieces of each item ----- these means 6 dictionaries, 6 books and 6 magazines.

(45*6) is already more than 252?

Please check your question with your source?

Best wishes

[YumYum]

Hi, can someone pls help with this Qn:


In a hall, 40% of the pupils are boys. After 10 girls left the hall, the percentage of girls decreased to 55%. How many boys are there in the hall?

Thanks!

[tianzhu]

YumYum:

Hi, can someone pls help with this Qn:


In a hall, 40% of the pupils are boys. After 10 girls left the hall, the percentage of girls decreased to 55%. How many boys are there in the hall?

Thanks!

Hi

The number of boys remained the same before and after.

At first
Boys : Girls -------- 2:3 (40%:60%) ------ 18:27

In the end
Boys : Girls -------- 9:11 (45%:55%) ------- 18:22

Make the units for boys the same

5 units ------- 10
1 unit ------ 2

Number of boys -------18*2 -------36

Best wishes

[portal]

1)I have this question to ask.A faulty weighing scale showed a reading of 0.3kg when nothing was placed on it. A box which contained 18 identical magazines was placed on the weighing scale, After 2/9 of the magazines were removed from the box, the weighing scale showed a reading of 7.82kg. The mass of each magazine was 60% the mass of the box. What is the mass of the box? Give your answer in grams. :?:

[portal]

Hope someone can help

[portal]

2)I have another question to ask.


3/4 of the fruits are apples and the rest are oranges.5/6 of the apples and 210 oranges were sold.The number of fruits left is 1/5 of the total.How many fruits were sold? :?:

[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:

[YumYum]

Dear Tianzhu,


Thank you.

I have another Qn:

The average mass of a group of girls is 38 kg. If one more pupil with a mass of 50 kg joins the group, the average mass will become 40 kg. Find the number of girls in the group first.

Thanks

[tianzhu]

portal:

1)I have this question to ask.A faulty weighing scale showed a reading of 0.3kg when nothing was placed on it. A box which contained 18 identical magazines was placed on the weighing scale, After 2/9 of the magazines were removed from the box, the weighing scale showed a reading of 7.82kg. The mass of each magazine was 60% the mass of the box. What is the mass of the box? Give your answer in grams. :?:

Hi

Number of magazines ------14(7/9*18)

7.82 - 0.3 ------- 7.52

1 magazine ------3 units
1 box ------ 5 units

(14*3) + 5 ------47

47 units ------ 7520
1 unit ------ 160

Mass of box ------5*160 ------800g

Best wishes

[tianzhu]

portal:

2)I have another question to ask.


3/4 of the fruits are apples and the rest are oranges.5/6 of the apples and 210 oranges were sold.The number of fruits left is 1/5 of the total.How many fruits were sold? :?:

Hi

For Q2, you may use UM or MD.

I’ll give you some pointers.

Use 40 units.

Apples sold -------- 25 units (5/6 of 30 units)
Apples left ------- 5 units

1/5 of fruits left ------- 1/5*40 -------8 units

Oranges left ------- 8-5 ------ 3 units

Oranges sold ------ 10-3 ------ 7 units

Oranges sold ------- 210

7 units ------ 210
1 unit ------- 30

32*30 ------- 960(number of fruits sold)

Best wishes