Q&A - P5 Math

[shawnlim88]

quekcc:

concerned1970:

Pls help me to solve last two pb sums. Tia

1) A frog is at the bottom of a well which is 31m deep. It climbs 6m up in the day and slides 4m down at night. How many days does it take for a frog to get out of the well?

2) Nathan withdrew 80% of his savings to purchase a laptop. If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account. A) How much did he pay for the laptop? B) How much did Nathan have in his savings account at first?

The answer for question 1 is 14 days.

The answer for question 2 is $2600 and $3250.

hi Concerned1970,
1) everyday the frog is up 2m
but he needs to be at 26m so that he can climb out of the well the next day ( he climbs 6m in daytime)
so 13 days is needed to climb to 26m so on 14th day, he is out of the well.

hope it helps
shawn lim

[shawnlim88]

Dear verykiasumummy,

verykiasumummy:

shawnlim88:

hi all,

2011-MGS-SA2-Paper2
Qn17
M, N, O shared the cost of rental flat. M paid 2/5 of the total amount paid by N and O. The ratio of the amount paid by N to the total amount paid by M and O is 1:3.
(a) what is the ratio of the rent paid by M to N to O? (8:7:13)
(b) given that M paid $35 more than N, how much rent did the 3 girls pay for the flat? (Ans:$980)
thank you

hi, offering my help :

M paid 2/5 of the total amount paid by N and O.
M : N + O
2 : 5 ------ x 4

The ratio of the amount paid by N to the total amount paid by M and O is 1:3
N : M + O
1 : 3 ------- x 7

both ratios are constant total. (1st ratio x 4, 2nd ratio x 7)

therefore :
M : N + O
8 : 20

N : M + O
7 : 21

M : N : O
8 : 7 : 13 (ans for a)


M : 8u
N : 7u
8u - 7u = 1u
1u --> $35
8u + 7u + 13u = 28u
28u --> $980 (ans for b)

thank you for your solution,
i finally understand the solution for (a).

oh boy, it is really a hard nut to crack.

have a great weekend.
shawn lim

[Muffins]

concerned1970:

Pls help me to solve last two pb sums. Tia

1) A frog is at the bottom of a well which is 31m deep. It climbs 6m up in the day and slides 4m down at night. How many days does it take for a frog to get out of the well?

2) Nathan withdrew 80% of his savings to purchase a laptop. If he were given a 15% discount on the cost price of the laptop, he could have put $390 back into his savings account. A) How much did he pay for the laptop? B) How much did Nathan have in his savings account at first?

For Q1, the frog advances 2m every day. On the 13th day, it reaches 26m, and on the 14th, it can actually exit, so the answer should be 14 days

For Q2, Nathan paid 85% of his 80% savings, which means that he paid 68%. That means 12% of his savings is $390. So $390 x (68/12) = $2210

(b) $390 x (100/12) = $3250

Hope I helped

[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.

[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!