Q&A - PSLE Math

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

Post by SOS mum » Tue Jan 28, 2014 8:30 pm

A painter was standing on the middle rung of a ladder to paint the external wall of a building. He moved up 5 rungs from there to paint the upper section of the wall. From there, he moved down 7 rungs to get a pole lying against the wall. Then he moved up another 6 rungs and remained there to clean up some dirt on the wall. He finally reached the top of the ladder when he went up to 5 more rungs to paint the uppermost section of the wall. How many rungs are there on the ladder?

SOS mum
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Re: Q&A - PSLE Math

Post by SOS mum » Tue Jan 28, 2014 8:45 pm

A boatman is trying to get upstream 13km. He paddles for 2 hours and rests for 1 hour. He manages to get upstream 3km in every hour that he paddles but each time he rests, the current will bring him backwards 1km. How many hours will he take to reach his destination? TIA

Er Jie
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Re: Q&A - PSLE Math

Post by Er Jie » Tue Jan 28, 2014 8:53 pm

Hi, I have a query:

The temperature of a cup of hot coffee was 70°C at 11.58a.m. Its temperature dropped by 3.5°C per minute. Its final temperature was 60% lower than the original temperature. At what time was the temperature 60% lower than the original temperature?

Answer provided by assessment book:
60% of 70°C = 60/100 x 70 = 42°C
Difference -> 70 – 42 = 28°C
3.5°C -> 1 min
28°C -> 8 min

11.58a.m. -> 12. 06p.m.
The temperature was 60% lower than the original temperature at 12.06p.m.

How do you interpret 60% lower than the original temperature?
Should the final temperature be 40% of 70°C = 28°C
or 60% of 70°C = 42°C ?

TIA.

sushi88
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Re: Q&A - PSLE Math

Post by sushi88 » Tue Jan 28, 2014 10:15 pm

SOS mum wrote:A painter was standing on the middle rung of a ladder to paint the external wall of a building. He moved up 5 rungs from there to paint the upper section of the wall. From there, he moved down 7 rungs to get a pole lying against the wall. Then he moved up another 6 rungs and remained there to clean up some dirt on the wall. He finally reached the top of the ladder when he went up to 5 more rungs to paint the uppermost section of the wall. How many rungs are there on the ladder?
M+5-7+6+6+5=15

15+15+1 =31

Oldschool
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Re: Q&A - PSLE Math

Post by Oldschool » Tue Jan 28, 2014 10:21 pm

Er Jie wrote:Hi, I have a query:

The temperature of a cup of hot coffee was 70°C at 11.58a.m. Its temperature dropped by 3.5°C per minute. Its final temperature was 60% lower than the original temperature. At what time was the temperature 60% lower than the original temperature?

Answer provided by assessment book:
60% of 70°C = 60/100 x 70 = 42°C
Difference -> 70 – 42 = 28°C
3.5°C -> 1 min
28°C -> 8 min

11.58a.m. -> 12. 06p.m.
The temperature was 60% lower than the original temperature at 12.06p.m.

How do you interpret 60% lower than the original temperature?
Should the final temperature be 40% of 70°C = 28°C
or 60% of 70°C = 42°C ?

TIA.
Hi,

You might want to take a look at this post from CIMMAN,

http://www.kiasuparents.com/kiasu/forum ... 2#p1000542


Regards


sushi88
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Re: Q&A - PSLE Math

Post by sushi88 » Tue Jan 28, 2014 10:26 pm

SOS mum wrote:A boatman is trying to get upstream 13km. He paddles for 2 hours and rests for 1 hour. He manages to get upstream 3km in every hour that he paddles but each time he rests, the current will bring him backwards 1km. How many hours will he take to reach his destination? TIA
2 hrs -> 6 km
1 hr rest -> 5km
2 hrs -> 5+6 = 11km
1 hr rest -> 10km
1 hr -> 13km

total -> 7 hours

SOS Mum, may I know the source of these questions?

SOS mum
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Re: Q&A - PSLE Math

Post by SOS mum » Tue Jan 28, 2014 10:47 pm

sushi88 wrote:
SOS mum wrote:A painter was standing on the middle rung of a ladder to paint the external wall of a building. He moved up 5 rungs from there to paint the upper section of the wall. From there, he moved down 7 rungs to get a pole lying against the wall. Then he moved up another 6 rungs and remained there to clean up some dirt on the wall. He finally reached the top of the ladder when he went up to 5 more rungs to paint the uppermost section of the wall. How many rungs are there on the ladder?
M+5-7+6+6+5=15

15+15+1 =31
Sorry, wld u mind explain why is there a need to add additional 6 n how do u derive 15? Many thks

sushi88
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Re: Q&A - PSLE Math

Post by sushi88 » Tue Jan 28, 2014 10:58 pm

SOS mum wrote:
sushi88 wrote:
SOS mum wrote:A painter was standing on the middle rung of a ladder to paint the external wall of a building. He moved up 5 rungs from there to paint the upper section of the wall. From there, he moved down 7 rungs to get a pole lying against the wall. Then he moved up another 6 rungs and remained there to clean up some dirt on the wall. He finally reached the top of the ladder when he went up to 5 more rungs to paint the uppermost section of the wall. How many rungs are there on the ladder?
M+5-7+6+6+5=15

15+15+1 =31
Sorry, wld u mind explain why is there a need to add additional 6 n how do u derive 15? Many thks
The highlighted part says that.

Is the answer correct?

ozora
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Re: Q&A - PSLE Math

Post by ozora » Tue Jan 28, 2014 11:16 pm

Need some help at the pattern.
458. 459. 925
568. 561. 123
220. 226 677
154. 158. 871
631. _____ 109
What the missing number?
Thanks

sushi88
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Re: Q&A - PSLE Math

Post by sushi88 » Tue Jan 28, 2014 11:54 pm

ozora wrote:Need some help at the pattern.
458. 459. 925
568. 561. 123
220. 226 677
154. 158. 871
631. _____ 109
What the missing number?
Thanks

The missing number is 631, correct?

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