Q&A - P4 Math

[chloecube]

[quote]

chloecube:

What is the sum of the first 30 even numbers?

2+4+6+8......+56+58+60=

I know there shld a a formula to solve such question.
Can anyone help?

I was told this kind of qns not in the p4 syllabus...maybe can find in MO or some enrichment schools programme. Is it true?[/quote]hi Nebbermind,

this question appear in DS school math process skill book

[Michaelia0816]

yes, of course could be found at!

[Nebbermind]

chloecube:

hi Nebbermind,

this question appear in DS school math process skill book

Thx!

[Michell0328]

mathnoobs:

John has 1/3 as many red marbles as blue marbles. If he bought 12 red marbles, he would have 2/5 as many red marbles as blue marbles. How many marbles did he have altogether ?

---------------------------------------------------------------------------------------I think is it 1/3 x 4/1 x 12/1=48/1
=48
:idea: :idea: :idea: :idea: :idea: :idea: :idea: :idea: :idea: :idea:

[Nebbermind]

Michell0328:

mathnoobs:

John has 1/3 as many red marbles as blue marbles. If he bought 12 red marbles, he would have 2/5 as many red marbles as blue marbles. How many marbles did he have altogether ?

---------------------------------------------------------------------------------------I think is it 1/3 x 4/1 x 12/1=48/1
=48
:idea: :idea: :idea: :idea: :idea: :idea: :idea: :idea: :idea: :idea:

Just saw this in Onsponge

For the benefit of those who do not have onsponge...

Initially, Red is 5U, Blue is 15U (Red : Bue is 1:3)
After adding in 12 Red, Red is 6U, blue is 15U (2:5).

Therefore 1U = 12, and the total marbles = 20U = 240.

[elisammom]

Pls help,


For every 4 beads that A has, B has 2 more beads than her. They have 60 beads altogether. How many beads does B have?

Thanks

[chloecube]

elisammom:

Pls help,


For every 4 beads that A has, B has 2 more beads than her. They have 60 beads altogether. How many beads does B have?

Thanks

A- 4 beads
B - 6 beads
1 group - 10 beads

60/10 = 6 groups
6 x 6 = 36

A - 24
B - 36

[ruohoo97]

Using guess and check method:


Let’s say A has 4, then B will have 6, obviously not equal to 60:
then try the following so on:

A B
4 6 not right
8 10 no
…
till
24 26 no
28 30 then you get 58, so you can conclude that A has 30, while B has 30.

I must say it is not clear whether B has 2 more than very 4 A has, or B has 2 more than A has.=(

[elisammom]

I used the guess and check method but the answer is not right.

The correct answer is 36, just like chloecube done.

I like to know why guess and check method is wrong in this question. Thanks

[elisammom]

Hi another question


24 coins are used to form a square. The number of coins on each side of the square is the same. Find the number of conins on each side of the square.

Ans: 7

Pls help. Thanks