Q&A - P5 Math

[doraemo]

hi,

Please help with these questions.

1)There were some white, black and red beads in a basket.
The number of white beads was 0.4 of the total number of beads. There were thrice as many black beads as red beads. If there were 18 red beads, how many white were there in the box?

2)Frank has 2/5 as many blue as red marbles. After buying another 42 blue and 42 red marbles, Frank then had 5/9 as many blue marbles as red marbles. How many marbles did Frank have at first?

[Maths Hub]

doraemo:

hi,

Please help with these questions.

1)There were some white, black and red beads in a basket.
The number of white beads was 0.4 of the total number of beads. There were thrice as many black beads as red beads. If there were 18 red beads, how many white were there in the box?

2)Frank has 2/5 as many blue as red marbles. After buying another 42 blue and 42 red marbles, Frank then had 5/9 as many blue marbles as red marbles. How many marbles did Frank have at first?

1) Red-> 18
Black -> 18 X 3 = 54
0.6 of total -> Red + Black = 54 + 18 = 72
0.2 of total -> 72 / 3 = 24
0.4 of total -> 24 X 2 = 48
White -> 48

2) This is a constant difference problem.
Initial
Red: Blue: Diff
5: 2 : 3

After
Red: Blue: Diff
9: 5: 4

Make the difference the same units (constant difference):
Initial
Red: Blue: Diff
5: 2 : 3
20: 8: 12

After
Red: Blue: Diff
9: 5: 4
27: 15: 12

Notice that both Red and Blue gained 7 units each.
7 units -> 42
1 unit -> 42 / 7 = 6

There are a total of 20+8 = 28 units at first.
Total -> 28 X 6 = 168

Cheers!

[doraemo]

Hi Maths Hub,


Thank you so much!

[Maths Hub]

sokk:

Hi,

I need help in these two questions. Appreciate very much!

1) Bookmarks are sold at 4 for $5 and pens are sold at 3 for $4.
Kenny bought an equal number of bookmarks and pens. He paid a total of $124.
How many bookmarks and pens did he buy altogether ?

1) The most important clue in this question is EQUAL NUMBER of bookmarks and pens.
Since bookmarks are sold in 4s and pens are sold in 3s, we need to find LCM of 3 and 4 which is 12.
Therefore 1 group of 12 bookmarks and 12 pens cost $5 X 3 + $4 X 4 = $31
Number of groups -> $124 / $31 = 4
Total number of bookmarks and pens -> 4 X 12 X 2 = 96
[quote]2) A pet farm had the same number of kittens, puppies and rabbits at first.
After 35 kittens, some puppies and rabbits were sold, there were 65 animals left.
There were thrice as many rabbits as puppies left.
There were 26 fewer kittens left than the rabbits left.
How many rabbits and puppies were sold ?[/quote]Rabbits left-> 3 units
Puppies left-> 1 unit
Kittens left-> 3 units - 26
Therefore total of 7 units - 26 is the 65 animals left.
7 units -> 65 + 26 = 91
1 unit -> 91 / 7 = 13
Rabbits left -> 13 X 3 = 39
Puppies left -> 13
Kittens left -> 13 X 3 - 26 = 13
Number of Rabbits at first = Number Puppies at first = Number of Kittens at first -> 13 + 35 = 48
Rabbits sold -> 48 - 39 = 9
Puppies sold -> 48 - 13 = 35

Cheers!

[sokk]

Hi Maths Hub, thanks a lot for the help!

[Jamesbond]

Three classes 4B, 4C& 4D donated some money to charity. The donation made by 4B was 1/3 as much as the total donation made by 4C and 4D. The donation made by 4C was 2/5 as much as the total donation made by 4B and 4D. If 4C donated $135 less than 4D, how much was collected from each class?

The ans is 4B-$189. 4C-$216. 4D-$351. Can somebody explain me how to derive it. Thx.

[dazzlego]

Jamesbond:

Three classes 4B, 4C& 4D donated some money to charity. The donation made by 4B was 1/3 as much as the total donation made by 4C and 4D. The donation made by 4C was 2/5 as much as the total donation made by 4B and 4D. If 4C donated $135 less than 4D, how much was collected from each class?

The ans is 4B-$189. 4C-$216. 4D-$351. Can somebody explain me how to derive it. Thx.

Hi Jamesbond,

B : C+D = 1:3 (Total: 4)
C : B+D = 2:5 (Total: 7)
Total is the same,
B : C+D = 7:21 (Total: 28)
C : B+D = 8:20 (Total: 28)

B -> 7 units
C -> 8 units
D -> 13 units

5 units -> $135
1 unit -> $27

4B: 7 untits -> $189
4C: 8 units -> $216
4D: 13 units -> $351

Cheers :celebrate:

[Jamesbond]

dazzlego:

Jamesbond:

Three classes 4B, 4C& 4D donated some money to charity. The donation made by 4B was 1/3 as much as the total donation made by 4C and 4D. The donation made by 4C was 2/5 as much as the total donation made by 4B and 4D. If 4C donated $135 less than 4D, how much was collected from each class?

The ans is 4B-$189. 4C-$216. 4D-$351. Can somebody explain me how to derive it. Thx.

Hi Jamesbond,

B : C+D = 1:3 (Total: 4)
C : B+D = 2:5 (Total: 7)
Total is the same,
B : C+D = 7:21 (Total: 28)
C : B+D = 8:20 (Total: 28)

B -> 7 units
C -> 8 units
D -> 13 units

5 units -> $135
1 unit -> $27

4B: 7 untits -> $189
4C: 8 units -> $216
4D: 13 units -> $351

Cheers :celebrate:

Thx Dazzlego. My DS just entering P5. Since ratio is new to him he finds it difficult to follow the steps. Can u pl help using some other method.

[Jamesbond]

:thankyou:

[ahxuan.031873ymail.031873com]

Hi,


My child has misplaced it. Anyone can email me a copy? Many Thanks.