Q&A - P5 Math

[dazzlego]

happyheart:

hi,

Please help with these questions.

1) Alice and Belle did not have any stickers at first.
After calvin gave 80% of his stickers to the two girls, he had 38 more stickers than Alice while Belle had 184 more stickers than him.
a) How many stickers did Calvin have at first?
b) Express Belle's stickers as a percentage of the total number of stickers. Round off your answer to the enarest whole number.
(not by algebra pls)


2) A snail is climbing up a tree trunk.
For every 5cm that it clims, it slips down by 1.5cm.
It takes 3 seconds to climb 1cm and 2 seconds to slip 1cm.
What is the distance it can climb in 6 minutes?
( Is there a particular concept pertaining to this kind of qns).

Thank you.

Hi happyheart,

1) U can draw the model out for a clearer view.
C= 1unit, B= 1unit+184, A= 1unit-38
Since 20% of C is 1unit, 100% of C is 5 units
1 unit + 1 unit + 184 + 1 unit - 38 = 5 units
3 units + 146 = 5 units
2 units -> 146
1 unit -> 73
a) Calvin at first -> 5 units -> 5 x 73 = 365
b) Belle -> 1 unit + 184 = 257
Percentage = (257/365) x 100% = 70.41...% = 70%

2) I called this concept 'grouping' or 'sets'
1 group / 1 set in this question is climbs 5 cm and slips 1.5 cm
Climb 5cm -> 15s
Slip 1.5cm -> 3s
Time taken to do 1 set -> 15s + 3s = 18s
Distance travelled in 1 set -> 5cm - 1.5cm = 3.5cm

6mins = 360s
360 ÷ 18 = 20 sets
20 x 3.5cm = 70cm

However, if the questions ask for the highest distance, the answer is not 70 cm. In this case, we should check the distance travelled in 19 sets (1 set less).
19 sets -> 3.5cm x 19 = 66.5cm
66.5cm + 5cm = 71.5cm (before the snail slips down)

Similar way of approach applied if the questions ask for the time needed for snail to climb 70 cm(the answer is not 6 minutes / 360 s)
19 sets -> 3.5cm x 19 = 66.5cm
70cm - 66.5cm = 3.5cm
5cm -> 15s
3 cm -> 10.5s
Time to do 19 sets -> 19 x 18s = 342s
342s + 10.5s = 352.5s

Hope it is not too confusing :?
Cheers :celebrate:

[usaik]

Hello,


I need help on the following question. Appreciate very much!
http://i50.tinypic.com/6is1sz.jpg\">

[Maths Hub]

usaik:

Hello,


I need help on the following question. Appreciate very much!
http://i50.tinypic.com/6is1sz.jpg\">

Hi,

First, find the breadth of the rectangle.
Breadth -> (56 – 18 – 18 ) ÷ 2 = 10 cm
Triangle ABY + Triangle BXY -> Triangle ABX -> Half of rectangle ABCD -> 10 × 18 ÷ 2 = 90 cm^2
Triangle BXY -> 90 – 42 = 48 cm^2

Hope it helps!

[usaik]

Maths Hub:

usaik:

Hello,


I need help on the following question. Appreciate very much!
http://i50.tinypic.com/6is1sz.jpg\">

Hi,

First, find the breadth of the rectangle.
Breadth -> (56 – 18 – 18 ) ÷ 2 = 10 cm
Triangle ABY + Triangle BXY -> Triangle ABX -> Half of rectangle ABCD -> 10 × 18 ÷ 2 = 90 cm^2
Triangle BXY -> 90 – 42 = 48 cm^2

Hope it helps!

Hi Maths Hub,

Thank you so much for your solution. May I know why is Triangle ABX = Half of triangle ABCD? Appreciate your kind advice very much. Thank you.

[Maths Hub]

usaik:

Maths Hub:

[quote=\"usaik\"]Hello,


I need help on the following question. Appreciate very much!
http://i50.tinypic.com/6is1sz.jpg\">

Hi,

First, find the breadth of the rectangle.
Breadth -> (56 – 18 – 18 ) ÷ 2 = 10 cm
Triangle ABY + Triangle BXY -> Triangle ABX -> Half of rectangle ABCD -> 10 × 18 ÷ 2 = 90 cm^2
Triangle BXY -> 90 – 42 = 48 cm^2

Hope it helps!

Hi Maths Hub,

Thank you so much for your solution. May I know why is Triangle ABX = Half of triangle ABCD? Appreciate your kind advice very much. Thank you.[/quote]Hi,

Area of Triangle -> 1/2 X Base X Height
Area of Triangle ABX -> 1/2 X AB X BC = 1/2 X (AB X BC) = 1/2 X Area of Rectangle ABCD

Area of Rectangle ABCD -> 18 X 10 = 180 cm^2
Area of Triangle ABX -> 1/2 X 18 X 10 = 90 cm^2
Cheers!

[usaik]

Hi Maths Hub,


Got it. Thank you so much!

[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 ?

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 ?

[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!