Correct me if I am wrong, but

840/2800 x 100% is the correct answer because percentage decrease is compared to what was at first/original which in this case was last year.

Hi need help with this qn.

Has anyone posted it yet? pl direct me to the page. Thanks.

A, B and C were standing in a straight line waiting for a race to start.
C was 300 m ahead of B and B was 100 m ahead of A. At 9 am, they started the race. A overtook B in 5 min. In another 5 min, A overtook C. If B's speed is 150 m/min, at what time did B overtake C?

Thanks in advance.

…

tianzhu:

Hi maths6a


Just curious, where are your two questions from? They don’t look like questions from past years papers.
[quote]If Andy runs up 7 steps of the escalator, he will take 36 sec to reach the top of the escalator. If he runs up 13 steps, he will take him only 27 sec to reach the top. How many seconds would it take him to reach the top if he did not run up any steps of the escalator at all?

If Andy runs up 7 steps, he needs 36 seconds to reach the top of the escalator.

If he runs up 13 steps, he needs 27 seconds to reach the top the escalator .

36-27 ----- 9
Therefore each additional step takes 9/6 -------1.5 seconds

Total steps in escalator = 7 + 36 /1.5 ----- 31

or 13 + 27/1.5 ------ 31

If he did not run up any steps, he will take 31*1.5 ------ 46.5 seconds.
[quote]When asked how many gold coins a miser had, his reply was, \" If I divide the coins into 2 unequal numbers, then 49 times the difference between the two numbers equals the difference between the squares of the two numbers.\"
How many coins did he have? [/quote]The second question involves difference of squares formula.

a2 - b2 = (a + b) (a - b) (a2 means a to the power of 2)

Given a2 - b2 = 49(a-b)

Therefore (a+b) (a-b) = 49(a-b)
Hence (a+b) =49

Use listing or GC
Try a=25, b=24
625-576 = 49(25-24)

There are 49 coins[/quote]Wow, what kind of questions are these? They are just 2 of the questions in my P4 neighbour's worksheet over the september holidays! Managed to help her with the rest but have no clue how to help her with these 2 so better check with the experts here. Thanks!

Dear Gurus out there, need help with 2 questions:-


1. If Andy runs up 7 steps of the escalator, he will take 36 sec to reach the top of the escalator. If he runs up 13 steps, he will take him only 27 sec to reach the top. How many seconds would it take him to reach the top if he did not run up any steps of the escalator at all?

2. When asked how many gold coins a miser had, his reply was, " If I divide the coins into 2 unequal numbers, then 49 times the difference between the two numbers equals the difference between the squares of the two numbers."
How many coins did he have?

Thank you in advance fof the solution.

Carrot:

hi

tough question here pleasee help

john shifted the decimal point onumber twice to the left to obtain a new number. the difference between thr new number and the original number was 136.62
a) How many times of the new number is the original number?
b) What is the sum of the 2 numbers ?

To better understand this question, take 100 as the original number. When you move its decimal place to the left 2 places, the number becomes 1.
so the original number is 100 units and the new number will be 1 unit.
The sum between the 2 numbers will be 101 units and the difference between them will be 99 units.

a) the new number is 100 times the new number.

99 units --- 136.62
101 units --- 101 x 136.62 /99
= 139.38

super star:

hi

I went through the problem & the working .but still cannot understand that.please explain this problem

maths6a:

[quote=\"beauty queen\"]Please help me with this question,

There are some black and white marbles in a bag. If 20 black marbles are removed from the bag, the total number of marbles left will be 7 times the number of black marbles left. If 50 white marbles are removed from the bag, the total number of marbles left will be 5 times the number of black marbles left. How many marbles are there in the bag.

Using algebra which in this case is cross multiplication:
When you remove 20 black marbles, the ratio of total marbles left to black marbles left is 7 : 1 so
white to black will be 6 : 1.
so number of white to black at first will be
6 units : 1 unit + 20
then question says to remove 50 white marbles are from the bag so
whilte --- 6 units - 50 ------- 4 equation 1
black ---- 1 unit + 20 -------1 equation 2
multplying equation 2 by 4 because the LCM of 1 and 4 is 4,
equation 2 becomes 4 units + 80
so now 6 units - 50 ---- 4 units + 80
2 units = 80 + 50 = 130
1 unit = 65
number of marbles in the bag = 7 units + 20
= 475
Hope this method is easier for you?






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[/quote]

acehkr3009:

Hi all,


Here is a Before & After question that I come across on one assessment....

Yesterday, Peter has 689 Singapore and Malaysia stamps. This morning, he used 2/5 of his Singapore stamps to exchange for 31 Malaysia stamps. As a result, he now has equal number of Singapore and Malaysia stamps. How many Malaysia does he has yesterday?

Can someone used Model and algebra to solve this question.

Appreciate with Thanks.

Since no one has helped with this one, let me try.

Since 2/5 of S'pore stamps used, there will be 3/5 of S'pore stamps left.
Since Sing = Malaysian after 31 Malaysian added, we start with 3 units for Sing and Malaysian.
S ---- 3 units + 2 units = 5 units at first
M ---- 3 units - 31 at first
5 units + 3 unit - 31 = 689
8 units = 689 + 31
8 units = 720
1 unit = 90
3 units - 31 = 3 x 90 - 31 = 239
Let me know if you still need the model method.

Dear all,

Wrt the speed qn, now that someone explained that 1u is the average of the speed he’s travelling so + 10 and -10 will be the speed he was well and sick, I can now understand the solution.

But why is it when I use
40/x - 40/x +20 = 1/6 (x being the speed when he was not well and x + 20 being the speed when he was well), then I cannot solve from here?

I think one has to be very familiar with algebra to be able to use algebra but this is like way beyond a 12 year old?

I think in this case maybe the guess and check method is a better choice especially after one has spent some time trying to work out the various possible methods?
Thanks in advance for the time to explain.

beauty queen:

Please help me with this question,


There are some black and white marbles in a bag. If 20 black marbles are removed from the bag, the total number of marbles left will be 7 times the number of black marbles left. If 50 white marbles are removed from the bag, the total number of marbles left will be 5 times the number of black marbles left. How many marbles are there in the bag.

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