Q&A - PSLE Math

[Chan09]

Hi tianzhu,


This was the question given bybteacher as it is:
2) there are 480 people in Gp X and 20% are children. Of the 280 people in Gp Y, 70% are children. Some people moved from Gp Y to Gp X . At the end the no. of children in Gp Y and X are 50% and 40% respectively. How many people moved from Y to X?

Not sure if this can be solved?

[jarenchuatw]

A snail tried to crawl out from the bottom of a well. For every 4cm that it crawled, it slipped back by 1cm. It took 4 seconds to crawl 1cm, and 2 seconds to slip back.

(a) What was the height the snail climb in 2 minutes?
(b) What was the shortest time needed for the snail to climb 56cm?

[tianzhu]

Chan09:

Hi tianzhu,


This was the question given bybteacher as it is:
2) there are 480 people in Gp X and 20% are children. Of the 280 people in Gp Y, 70% are children. Some people moved from Gp Y to Gp X . At the end the no. of children in Gp Y and X are 50% and 40% respectively. How many people moved from Y to X?

Not sure if this can be solved?

Hi

Please check with the teacher.

If 280 is changed to 380,it's solvable.

Best wishes

[Winx5015]

Hi MathIzzzFun,


Thanks for your help

[Winx5015]

Hi, need help for the following questions.


Using make a list method
Q1). Mother had less than 3105 coins. If she put them equally into boxes of 24 or 36, she would have 15 coins left. How many boxes did she have if she arranged the coins into boxes of 30?

Using restating problem
Q2). 3 similar tables and 4 similar chairs cost $240. 2 such tables and 3 similar racks cost $115. 1 such chair and 2 such racks cost $95. How much do 2 such tables and 1 such chair cost altogether?

:thankyou:

[JGMum]

jarenchuatw:

A snail tried to crawl out from the bottom of a well. For every 4cm that it crawled, it slipped back by 1cm. It took 4 seconds to crawl 1cm, and 2 seconds to slip back.

(a) What was the height the snail climb in 2 minutes?
(b) What was the shortest time needed for the snail to climb 56cm?

I am no Math whiz, but can I try?


|-->|-->|-->|-->| 4s x 4 = 16 s
|<--| 2s

(a)
Total time taken for each \"cycle\" is (4x4)+2=18 sec. And net height travelled after each cycle is 3 cm (4cm - 1cm)

2 minutes = 120 secs
If we divide 120 sec by 18 secs, we get 6.667 \"cycles\", not a whole number. This means that after completing the 6th cycle, the snail travels for a bit more, and would not reach the 4 cm for \"sliding back\".
We look at the 6th cycle.
After 6th cycle, ht travelled = 3cm x 6 = 18cm, and time transpired = 6 x 18 s = 108 s.

120s - 108 s = 12 secs or 3 more cm from above diagram.
Hence total height travelled at the end of 2 min = 18cm + 3cm = 21 cm.

(b) We take 56 cm divided by net height of 3 cm, we get 18.667. This means that the snail can complete slightly more than 18 cycles, and then it will reach 56 cm.
We look at the 18th cycle again.
After 18th cycle, height travelled = 18 x 3cm = 54 cm, time transpired = 18sec x 18 cycles = 324 secs.
Another 2 cm (54cm + 2 cm = 56 cm) would take another 2 x 4 sec = 8 sec.
Shortest time taken to travel 56 cm height is therefore 324 s + 8 s = 332 sec.
In minutes, that would be 5 min and 32 sec. (332 divided by 60)

Hope the answer is correct. :xedfingers:

[jarenchuatw]

JGMum, a million tks to u. :salute: Ur definitely much better than me...

[JGMum]

You're welcome. Do you know if the answer is correct?

[small]

Hi,


My mind is block and I got 2 answer for this question. :stupid:

Please help and thanks in advance.
[quote]The spped of a car was 60 km/h abd the speed of a van was 45 km/h. They started from Town P at the same time and travelled along the same route towards Town Q. The car reached Town Q 1 hour 40 min earlier than the van. What was the distance travelled by the can when the car reached Town Q?[/quote]

[Chan09]

Hi TianZhu, if it is 380 can you explain the method to solve? Tks