Q&A - PSLE Math

[tianzhu]

iamproudparents:

http://i47.tinypic.com/1621qpk.jpg\">

Hi

At first
GF ------- 12 units
AF -------- 8 units

In the end
GF ------- 3 units
AF -------- 2 units

Number of fishes removed --------- 15 units -------- 150
1 unit ------- 10

Number of GF removed ------- 9 units -------- 90

Number of AF@first -------- 8 units -------- 80

Best wishes

[jieheng]

iamproudparents:

http://i47.tinypic.com/1621qpk.jpg\">

G 60u (60%)
A 40u (40%)

Also can use G --> 12u (60%) and A --> 8u (40%)

No of goldfish decreased by 75% , 75% of 60u --> 45u

No of angelfish was 1/4 of the original no of angelfish --> no of angelfish decreased by 3/4 --> 3/4 of 40u --> 30 u

total 150 fish were removed

45u + 30u --> 150
75u --> 150
1u --> 2

a)

No of goldfish were removed = 45u = 45*2 = 90

b)

No of angelfish were there at first = 40u = 40*2 = 80

[jieheng]

iamproudparents:

http://i45.tinypic.com/zlt204.jpg\">

B 5u
A 15u

After Anthony spent 1/3 of his money , he left 2/3
2/3 of 15u --> 10u

After Bill spent 3/5 of his money , he left 2/5
2/5 of 5u --> 2u

Anthoy had $130 more than Bill

10u - 2u --> 130
8u --> 130
1u --> 16.25

a)

5u--> 5*16.25 = 81.25
the money that Bill had at first = $81.25

b)

10u --> 10*16.25 = 162.5
the money that Anthony had left = $162.50

[jieheng]

iamproudparents:

http://i47.tinypic.com/24cejcm.jpg\">

B:C:D = 2:3:3

Bond received 1/6 of the total amount of sweets
2/12 (1/6) --> 2u

3/12 -->3u

B+C+D = 2/12 + 3/12 + 3/12 = 8/12

A = 1 - (B+C+D) = 1 - 8/12 = 4/12

Amos took 28 sweets for himself

4u --> 28
1u --> 7

12u --> 12*7 = 84

No of sweets were there in the bag at first = 84

[moonsun]

MathIzzzFun:

moonsun:

Hello.


Would be thankful if someone can teach me how I can solve this...

If 1/5 = 1/A + 1/B and A & B are whole numbers, what are the values of A & B?

1/5 = 1/5 - 1/6 + 1/6 = 1/30 + 1/6

cheers.

Hi Mathizzzfun,

Thank you for the workings.

But.... Sorry, how did you get 1/5-1/6 + 1/6?.... :nailbite:

[MathIzzzFun]

moonsun:

MathIzzzFun:

[quote=\"moonsun\"]Hello.


Would be thankful if someone can teach me how I can solve this...

If 1/5 = 1/A + 1/B and A & B are whole numbers, what are the values of A & B?

1/5 = 1/5 - 1/6 + 1/6 = 1/30 + 1/6

cheers.

Hi Mathizzzfun,

Thank you for the workings.

But.... Sorry, how did you get 1/5-1/6 + 1/6?.... :nailbite:[/quote]this is a common \"trick\" taught to MO students to solve questions like :
1/2 ( 1 + 1/3 +1/6 + 1/10 + 1/15......+1/5050)

cheers.

[MathIzzzFun]

thoughtfulminds:

Zai ah MathIzzFun !


Are you a teacher?

math tutor .. cheers.

[mama_10]

Hi,


Need help for below question.
There were 50 questions in a Maths test. Sam answered 85% of them correctly while Nicky answered 80% of them correctly. How many percent more questions did Sam answer correctly than Nicky ?

My kid said how come Sam answered 42.5 question correctly?

Thank you.

[MathIzzzFun]

mama_10:

Hi,


Need help for below question.
There were 50 questions in a Maths test. Sam answered 85% of them correctly while Nicky answered 80% of them correctly. How many percent more questions did Sam answer correctly than Nicky ?

My kid said how come Sam answered 42.5 question correctly?

Thank you.

..cute... well, it is possible that Sam answered part 1 of a 2-part question correctly. Since the question is on percentage, the total number of questions is not important. The question can be changed to :

\"In a Maths test. Sam answered 85% of them correctly while Nicky answered 80% of them correctly. How many percent more questions did Sam answer correctly than Nicky ?\"

cheers.

[mama_10]

Haha!

My kid can get al the paper 2 questions correct but make careless mistake on multiple choice.
How to ‘cure’?
btw, what’s the answer for that question?
Thank you.