Q&A - PSLE Math

[dicoyote]

Hi MathIzzzFun,


Thanks for the solution, though pardon me for question, I understand why the uses of \"x3\" for the values, though need a little more help on the explanation on this equations, am a bit lost, thanks

\"(500 x 22.5 - 11025) ÷ 12.5\"[/quote]

3 vases delivered late --> $10 -- 30 units (3 units/$1), 1 vase delivered late --> 10 units
2 vases delivered on time --> $ 15 --- 45 units, 1 vase delivered on time --> 22.5 units
$3675 --> 11025 units

question now becomes :
Total number of vases delivered = 500 (**think: total number of animals)
1 vase delivered on time --> 22.5 units (**think: 1 cow --> 4 legs)
1 vase delivered late --> 10 units (** think: 1 chicken --> 2 legs)
22.5 units - 10 units = 12.5 units (**think: 4-2 = 2 legs -- difference in number of legs)
(difference in amount collected)
Total amount collected --> 11025 units (**think: total number of legs)

All vases delivered on time --> 22.5 units x 500 = 11250 units (**think: all are cows)
11250 - 11025 = 225 units, extra amount collected if all delivered on time (think: extra legs if all are cows)
Number of vases delivered late = 225 units / 12.5 units = 18

using assumption method:
for every 6 vases delivered time, amount collected = 6/2 x $15 = $45
for every 6 vases delivered late, amount collected = 6/3 x $ 10 = $20

If all delivered on time, amount collected = 500/2 x $ 15 = $3750
$3750 - $3675 = $75
Number of vases delivered late = $75 / ($45-$20) x 6 = 18

cheers.[/quote]

Hi MathIzzzFun,

Thank you so much, am amazed at the details you have provided, not only that, even applying side by side with the \"chicken & cow\" logic, which make understanding more easier

Just to clarify my understanding, the \"x3\" uses across for the value is to find a similarity basis for the equation, am I correct? :scratchhead:

[charsen]

How to solve this question ?

The sum of 4 numbers is 80.If you add 3 to the first number, subtract 3 from the second number,multiply the third number by 3 d divide the fourth number by 3,the result will be equal.What is the difference between the largest and the smallest of the original numbers.

[tianzhu]

charsen:

How to solve this question ?

The sum of 4 numbers is 80.If you add 3 to the first number, subtract 3 from the second number,multiply the third number by 3 d divide the fourth number by 3,the result will be equal.What is the difference between the largest and the smallest of the original numbers.

Hi

First thing first, is such a question within the syllabus?

The original numbers are 12,18,5 and 45.

Difference ------ 45-5 ------ 40

Best wishes

[tianzhu]

Michaelia0816:

A train 210m long was travelling at 90km/h and it overtook a train travelling 72km per hour in 55s. What was the length of the second train?

Hi girl

From some of the questions posted by you, it’s safe to assume that you are in the top class in your school.

Your school teacher has been giving you some pretty interesting questions if those questions are from your homework.

Let's give a slight tweak to your train question. Instead of moving in the same direction, change it to moving in opposite direction.

Two trains, A and B are travelling in opposite direction at 90km/h and 72km/h. The length of train A is 210m. If they cross each other in 8 seconds, find the length of the train B?

Try it only when you’ve completed all your homework.

Best wishes

[Michaelia0816]

A square is incribed in a circle. If the area of the square is 70cm2, what the area of the circles? (Take pi as 22/7)

[Michaelia0816]

Tianzhu,of course that our class is top, this is of course my homework, it even can photo it and post it on twitter.

[Michaelia0816]

Tianzhu, pls help with the question on top of my pervious post, it my last question!

[tianzhu]

Michaelia0816:

A square is incribed in a circle. If the area of the square is 70cm2, what the area of the circles? (Take pi as 22/7)

Hi

Please take a look at this similar question.

Area of the outer square ------ 140

140 ------ d*d where d is the diameter of the circle.

Area of circle -----pi*d^2/4 ----- 22/7*140/4 ------ 110

Hope this helps.

Best wishes

http://farm7.staticflickr.com/6151/6191262010_71cc0ec1fd_z.jpg\">

[Michaelia0816]

Do the 140cm2 get by 70cm2*2

[Michaelia0816]

Now I understand how 140cm2 is get