## Q&A - PSLE Math

### Re: Q&A - PSLE Math

Please help

Kathy had 7 bags of rice at first. Then she bought a bag of rice with the mass of 24.9 kg and another bag of rice with mass of 17.6 kg . As a result , the average mass of the bags of rice increased by 2.5 kg what was the total mass of the 9 bags of rice?

Kathy had 7 bags of rice at first. Then she bought a bag of rice with the mass of 24.9 kg and another bag of rice with mass of 17.6 kg . As a result , the average mass of the bags of rice increased by 2.5 kg what was the total mass of the 9 bags of rice?

### Re: Q&A - PSLE Math

MR TAN -> 8K+10COOKIE64 wrote:Mr Tan is (8k+10) years old now. How has two children , Rosalynn and David . Mr Tan is twice as old as Rosalynn now. David is 2k years younger than Rosalynn. How old will Mr Tan be when David turns 18 years old?

ROSALYNN -> 4K+5

DAVID -> 2K+5

This is a constant different question.

Difference in age ->8K+10-2K+5 = 8K-2K + 10-5

= 6K+5

As the difference will always be 6k+5, we can say that if David is 1 year old, Mr tan will be 6K+5 years older than him, if David is 2 years old, Mr tan will still be 6K+5 years older than him, so when David is 18 years old, Mr tan will still be 6K+5 older than him.

18+6K+5=

**6k+23 years old**

- PlayfulFairy
- BlueBelt
**Posts:**268**Joined:**Tue Oct 07,**Total Likes:**2

### Re: Q&A - PSLE Math

Please help! Thanks!

At a sale, Mr Lim bought 10 mugs of the same kind. His sister bought 8 such mugs. She also bought 3 towels at $2.50 each. Altogether, she spent $2.30 less than Mr Lim. What was the total amount of money Mr Lim and his sister spent?

At a sale, Mr Lim bought 10 mugs of the same kind. His sister bought 8 such mugs. She also bought 3 towels at $2.50 each. Altogether, she spent $2.30 less than Mr Lim. What was the total amount of money Mr Lim and his sister spent?

### Re: Q&A - PSLE Math

After seeing Nerdymath's solution. I understood the the answer.COOKIE64 wrote:Hi , the answer is 6K+ 23 years old Mr tan will be

Last edited by Ender on Tue Sep 29, 2015 5:01 pm, edited 1 time in total.

### Re: Q&A - PSLE Math

Now,COOKIE64 wrote:Please help with these Q

Mrs Tan is 40 years old and her son is twice her daughters' sage. Mrs Lim will be thrice her Sons's age when her daughter is 12 years old .how old will Mrs Lim be when her 2 children's combined age equals to her age ?

Lim = 40 yrs

Son =2d

Daugther =d

When the daughter is 12 years old, number of years passed is (12-d) years

Daughter = 12

Son = 12 + d , Constant difference

Lim = 36 + 3d(Triple of Son) or 40 + (12 -d)

3d + 36 =52 - d

4d = 16

d = 4

Son = 8 , 2 times of daughter.

Let the number of years pass to be 'u'

(Daughter + u) + (Son +u) = (Mrs Lim + u )

(4+u) +(8+u) = (40+ u)

12 + 2u = 40 + u

u = 28

In 28 years time

Edit note: The answer is 68 years old, from 40 +28

Last edited by Ender on Wed Sep 30, 2015 9:28 am, edited 3 times in total.

### Re: Q&A - PSLE Math

9* 2.5kg=22.5kgCOOKIE64 wrote:Please help

Kathy had 7 bags of rice at first. Then she bought a bag of rice with the mass of 24.9 kg and another bag of rice with mass of 17.6 kg . As a result , the average mass of the bags of rice increased by 2.5 kg what was the total mass of the 9 bags of rice?

24.9kg+17.6kg=42.5kg

42.5kg-22.5kg=20kg

20kg/2=10kg

10kgx7=70kg

70kg+42.5kg=112.5kg

Solved by DS.

Last edited by NerdyMath on Tue Sep 29, 2015 5:25 pm, edited 1 time in total.

### Re: Q&A - PSLE Math

You're welcome! DS is very happy to help!COOKIE64 wrote:Ok Thanks to all for helping me

### Re: Q&A - PSLE Math

Don't forget the power of models this Fri. Good luck to all!PlayfulFairy wrote:Please help! Thanks!

At a sale, Mr Lim bought 10 mugs of the same kind. His sister bought 8 such mugs. She also bought 3 towels at $2.50 each. Altogether, she spent $2.30 less than Mr Lim. What was the total amount of money Mr Lim and his sister spent?

- mceducation1
- GreenBelt
**Posts:**107**Joined:**Mon Dec 24,**Total Likes:**6

### Re: Q&A - PSLE Math

bhfg0302 wrote:Help

Hi there,

Let's start with the following:

Information Given:

Dave gave 50% of the no. of his 50-cents' coins to Wayne

Wayne gave 50% of the no. of his $1 coins to Dave

After buying a buy with some $1 coins, the ratio of the no. of coins Dave had was:

No. of 50-cents coins : No. of $1 coins

1 : 2

After buying a books with some 50-cents, the ratio of the no. of coins Wayne had was:

No. of 50-cents coins : No. of $1 coins

1 : 5

Let's call the no. of 50-cents coins Dave has in the end "1 unit"

thus the no. of 50-cents coins Dave had in the end:

1 unit = 10 + 1 part

(10 represents the 10 coins Wayne had used to buy the book

$5 = 10 50-cents coins

and 1 part represents the no. of 50-cents coins Wayne had left)

No. of $1 coins:

Since the ratio of the no. of 50-cents coins Wayne had to that of the no. of $1 coins he had in the end was 1 : 5

Thus the no. of $1 coins Wayne had in the end was:

5 parts = 2 units + 16

(2 units --- becos the ratio of Dave's 50 cents coins to $1 coins was 1 : 2

and Dave had used $16 to buy a bag - which is 16 coins)

since 1 unit = 10 + 1 part

therefore 2 units = 20 + 2 parts

Thus 5 parts = 2 units + 16

is the same as 5 parts = (20 + 2 parts) + 16

5 parts = 36 + 2 parts

5 parts - 2 parts = 36

3 parts = 36

1 part = 36 divided by 3 = 12

Since Wayne had used 10 coins to buy a book,

10 + 12 = 22

Since Dave had given half of his 50 cents coins away,

Therefore there were 2 x 22 = 44 fifty cents coins

44 x 50cents = $22

Therefore the original amount that Dave had was $ 22.

Hope this helps!

SMILE!!

Michelle Choo

Mathematics Educator for 27 years