Tutor MathsGuru: Ask me for your burning Maths questions!

[wkong]

Hi All,


Need helps for the following questions:

1. Last year, the enrolment of school X was 90% that of school Y. This year, the enrolment of school X decreased by 220 while that of school Y increased by 200. In the end, the enrolment of school X is 70% that of school Y this year, what was the enrolment of each school last year?

2. Daniel’s savings was 75% as much as Annabel. After Annabel saved another $40 and Daniel saved another $20, Daniel’s savings became 5/8 as much as Annabel’s savings. Find Daniel’s savings at first.

3. A farmer had 5/8 as many chickens as ducks at first. After selling 50 chickens and 8 ducks, he had 25% as many chickens and ducks. How many ducks did the farmer have at first?

4. In May, Mrs Tan’s salary was 90% of Mrs Ismal’s salary. In June, Mrs Tan’s salary increased by $400 while Mrs Ismal’s salary increased by $600. If Mrs Tan’s salary became 80% of Mrs Ismal’s salary, what was Mrs Tan’s salary in May?

Thanks.

[Vanilla Cake]

wkong:

1. Last year, the enrolment of school X was 90% that of school Y. This year, the enrolment of school X decreased by 220 while that of school Y increased by 200. In the end, the enrolment of school X is 70% that of school Y this year, what was the enrolment of each school last year?

Last year
School X : School Y
90% : 100%
9u : 10u

This year
School X : School Y
9u-220 : 10u+200
70% : 100%
7 : 10

10(9u-220)=7(10u+200)
90u-2200=70u+1400
20u=3600
u=180

Last year
School X -> 9u= 9x180=1620
School Y -> 10u=10x180=1800

Last year, the enrolment of school X and school Y was 1620 and 1800 respectively.

wkong:

2. Daniel's savings was 75% as much as Annabel. After Annabel saved another $40 and Daniel saved another $20, Daniel's savings became 5/8 as much as Annabel's savings. Find Daniel's savings at first.

Before
D : A
75% : 100%
3 : 4

Change
D : A
+20 : +40

After
D : A
5 : 8

D : A
3u : 4u
+20 : +40
5p : 8p

D : A
24u : 20u
+160 : +200
40p : 40p

24u+160=20u+200
4u=40
u=10

At first, Daniel's savings = 3u = 3x10 = $30

[Vanilla Cake]

wkong:

Hi All,

Need helps for the following questions:

Hi wkong,
Your questions sound familiar as I believe that I have seen them somewhere but cannot recall them at this moment. Could you pls advise the source of these 4 questions?

wkong:

3. A farmer had 5/8 as many chickens as ducks at first. After selling 50 chickens and 8 ducks, he had 25% as many chickens and ducks. How many ducks did the farmer have at first?

Before
C : D
5u : 8u

Change
Sold 50 chickens and 8 ducks

After
C : D
25% : 100%
1p : 4p

C : D
5u : 8u
-50 : -8
1p : 4p

C : D
20u : 8u
-200 : -8
4p : 4p

20u-200=8u-8
12u=192
u=16

8u = 8x16=128
At first, number of ducks = 128.

wkong:

4. In May, Mrs Tan's salary was 90% of Mrs Ismal's salary. In June, Mrs Tan's salary increased by $400 while Mrs Ismal's salary increased by $600. If Mrs Tan's salary became 80% of Mrs Ismal's salary, what was Mrs Tan's salary in May?

May
Mrs Tan : Mrs Ismail
90% : 100%
9 : 10

Change
Mrs Tan : Mrs Ismail
+400 : +600

June
Mrs Tan : Mrs Ismail
80% : 100%
4 : 5

Mrs Tan : Mrs Ismail
9u : 10u
+400 : +600
4p : 5p

Mrs Tan : Mrs Ismail
45u : 40u
+2000 : +2400
20p : 20p

45u+2000=40u+2400
5u=400
u=80

9x80=720

Mrs Tan's salary in May = $720

wkong:

Thanks.

You are welcome. Appreciate if you can advise the source as I am compiling these questions in order to prepare my younger sister who will be taking PSLE 2011 Maths exams.
Thks.

[wkong]

Wow, you are a good sister. My son is taking PSLE too in 2011. The source is ThinkingMath@onSponge - Conquer Problem Sums assessment book

[capricorn28]

Hi iFruit and Vanilla Cake


Thank you for your answers. Will let you know if the answers are correct after my daughter gets back with the right answers.

[Almighty]

Hi Dharma Sir,


I had posted a message to u. Pl.c 2 it when u r free.

[pineapple tarts]

Hi there,


The difference between 2 numbers is 66. When you divde the bigger number by the smaller number, the quotent is 7. What is the bigger number?

I found the answer using algebra. But how do I teach my P3 the correct way? Pls help me. thank you very much.

[iFruit]

pineapple tarts:

Hi there,


The difference between 2 numbers is 66. When you divde the bigger number by the smaller number, the quotent is 7. What is the bigger number?

I found the answer using algebra. But how do I teach my P3 the correct way? Pls help me. thank you very much.

Model diagrams may be better to start off with...

one box = smaller number
7 boxes = bigger number.

6 boxes = 66

1 box = 11; 7 boxes = 77.

[Almighty]

Dharma sir,


Pl.c for a message sent 2 yr inbox again.
Thnks

[Hifive]

Hi everyone


Need help with this P5 question:

The total of 4 numbers was 390. When the first number was tripled, the second number halved, the third number increased by 28 and the 4th number decreased by 15, the 4 numbers became equal. Find the original value of each number.

Thanks in advance.