Q&A - PSLE Math

Academic support for Primary 6 and PSLE
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Ender
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Re: Q&A - PSLE Math

Post by Ender » Mon May 23, 2016 9:34 pm

SOS mum wrote:Hi all, ps help. Many tks and God Bless:)
(2) At a fun-raising event, 60% of the people were male and the rest were female. 20% of the female left the event in the afternoon. In the evening, after 33 male and 35 female left the event, 75% of the people at the event were male.
(a) What percentage of the people left the event in the afternoon?
(b) How many people were there at the start of the fun raising event?
At the start, let the total of male and female = 100u

Code: Select all

Male: Female
60u : 40u
20% of 40u of female left the party = 8u

a) % of people left = 8u/100u X 100 = 8% ###

b)

Code: Select all

Male : Female
60u  : 32u
-33    -35
75p  : 25p
60u - 33 = 75p
32u - 35 = 25p
96u - 105 = 75p

96u - 105 = 60u -33
36u = 72
u = 2

At the start there are 100u = 200 people ###

sushi88
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Re: Q&A - PSLE Math

Post by sushi88 » Mon May 23, 2016 9:49 pm

wilburlim wrote:Someone help me for this question please. :gloomy: :thankyou:

The Robotics Club had twice as many pupils as the Science Club. The ratio of the number of girls to the number of boys in the Robotics Club was 4:1. The ratio of the number of girls to the number of boys in the Science Club was 2:3.
(a) Find the ratio of the number of girls in the Robotics Club to the number of girls in the Science Club.
(b) After 38 girls left the Robotics Club to join the Science Club, the ratio of the number of girls to the number of boys in the Science Club became 9:4. How many girls were in the Science Club in the end?
Club--------------G----------B
R-club initial-----8u---------2u (4:1)
S-club initial-----2u---------3u
After rec 38, S--2u+38-----3u
New ratio for S---9----------4

(a) Ratio of R-girls : S-girls is 8u : 2u = 4: 1

(b) (2u+38)/3u -> 9/4
8u + 152 -> 27u
19u -> 152
u->8
Hence girls in S club in the end is 2(8)+38 = 54

Jmaths.SG
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Re: Q&A - PSLE Math

Post by Jmaths.SG » Mon May 23, 2016 10:24 pm

SOS mum wrote:Hi all, ps help. Many tks and God Bless:)

(1) James used 4/7 of his screws and 3/5 of his nails to construct a wooden cupboard. In the end, he had an equal number of screws and nails left. Given that James had a total of 145 screws and nails at first, how many nails did he use to construct the wooden cupboard?
Solution with video in the following link:
https://www.facebook.com/permalink.php? ... 4939707325

happy to be mum
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Re: Q&A - PSLE Math

Post by happy to be mum » Tue May 24, 2016 11:58 pm

need help..

A circular wheel of diameter 35cm makes 100 revolutions in 1 minute. Calculate the distance covered by the wheel in half an hour. Express your answer in km.

MathWithModels
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Re: Q&A - PSLE Math

Post by MathWithModels » Wed May 25, 2016 8:59 am

Question:

A circular wheel of diameter 35cm makes 100 revolutions in 1 minute.
Calculate the distance covered by the wheel in half an hour. Express your answer in km.


Answer:

Radius of the wheel: 35 / 2 = 17.5 cm
Circumference of the wheel: 2 x Pi x Radius = 2 x 3.14 x 17.5 cm = 109.9 cm
Distance covered by the wheel in 1 minute = 109.9 x 100 = 10990 cm
Distance covered by the wheel in half an hour = 10990 x 30 = 329700 cm = 3.297 km

Thanks, Ender, for pointing out the mistake. Fixed now.
Last edited by MathWithModels on Wed May 25, 2016 5:26 pm, edited 1 time in total.


SOS mum
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Re: Q&A - PSLE Math

Post by SOS mum » Wed May 25, 2016 11:38 am

Thank you very much, Ender :rahrah:

SOS mum
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Re: Q&A - PSLE Math

Post by SOS mum » Wed May 25, 2016 11:40 am

Ender wrote:
SOS mum wrote:Hi all, ps help. Many tks and God Bless:)
(2) At a fun-raising event, 60% of the people were male and the rest were female. 20% of the female left the event in the afternoon. In the evening, after 33 male and 35 female left the event, 75% of the people at the event were male.
(a) What percentage of the people left the event in the afternoon?
(b) How many people were there at the start of the fun raising event?
At the start, let the total of male and female = 100u

Code: Select all

Male: Female
60u : 40u
20% of 40u of female left the party = 8u

a) % of people left = 8u/100u X 100 = 8% ###

b)

Code: Select all

Male : Female


60u  : 32u
-33    -35
75p  : 25p
60u - 33 = 75p
32u - 35 = 25p
96u - 105 = 75p

96u - 105 = 60u -33
36u = 72
u = 2

At the start there are 100u = 200 people ###
Thank you very much, Ender

Nebbermind
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Re: Q&A - PSLE Math

Post by Nebbermind » Wed May 25, 2016 3:41 pm

MathWithModels wrote:Question:

A circular wheel of diameter 35cm makes 100 revolutions in 1 minute.
Calculate the distance covered by the wheel in half an hour. Express your answer in km.


Answer:

Radius of the wheel: 35 / 2 = 17.5 cm
Circumference of the wheel: 2 x Pi x Radius = 2 x 3.14 x 17.5 cm = 109.9 cm
Distance covered by the wheel in 1 minute = 109.9 x 60 = 6594 cm
Distance covered by the wheel in half an hour = 6594 x 30 = 197820 cm = 1.9782 km
it's 100rpm...no?

cindy28
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Re: Q&A - PSLE Math

Post by cindy28 » Fri May 27, 2016 12:46 pm

need help with the following questions :thankyou:

Q1. Arnold and Sandy were given some money each. If Arnold spent $25 and Sandy spent $75 each day, Arnold would still have $2100 while Sandy would have spent all her money. If Arnold spent $75 and Sandy spent $25 each day, Arnold would still have $900 while Sandy spent all her money. How much money was given to each of them?

Q2. At first Edwin had some $10 and $2 notes in the ratio of 3 : 8. After exchanging 2 $10 notes for $2 notes, the ratio of $10 to $2 becomes 1 : 3. How much did money did Edwin have at first?

Q3. There are 260 students in a school. 30% of them were girls while the rest were boys. When the school reopened, more student were admitted. The new students had boys and girls in the ratio of 5 : 4. After new students were admitted, 40% of the students was girls.
a. How many girls were admitted?
b. How many students were there in the end?

Ender
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Re: Q&A - PSLE Math

Post by Ender » Fri May 27, 2016 1:52 pm

cindy28 wrote:need help with the following questions :thankyou:

Q1. Arnold and Sandy were given some money each. If Arnold spent $25 and Sandy spent $75 each day, Arnold would still have $2100 while Sandy would have spent all her money. If Arnold spent $75 and Sandy spent $25 each day, Arnold would still have $900 while Sandy spent all her money. How much money was given to each of them?
Scenario 1 :Spending Ratio
A : S
25 : 75

Total Arnold had = 25u + $2100
Total Sandy had = 75u ->She spent all, which is also what she had

Scenario 2 Sepnding Ratio
A : S
75 : 25

Total Arnold had = 75p + $900
Total Sandy had = 25p

25p=75u , Base on Sally's money
75p = 225u

25u + 2100 = 225u + 900 , Base on what Arnold had
200u = 1200
u = 6

Arnold had 25u + 2100 = $2250 #####
Sally had 75u = $450 #####

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