f2 maths 急要答案,快入!!
2012-01-31 7:02 am
(1) Peter shares stamps with Ann in the ratio 1:2.Ann shares her stamps with her brother in the ratio 3:2.Her brother gets 8 stamps.How many stampsare there in the beginning?
(2) Collin and Chris share the typing work of a document such that they both finish their portion of the document in 5 minutes.It is given that Collin types at 45 words per minute,and the ratio of Collin's typing speed to that of Chris is 9:10.
(a) How many words are there in the entire document?
(b) If they share a document by allocating an equal of words to each person,what is the ratio of the time by Collin to the time taken by Chris?
(3) The length of a certain road is Acm on a map of scale 1:25000 and Bcm on a map of scale 1:75000.What is the ratio of A to B?
(4) A woman rides a horse from village P to village Q at a speed of 24km/h. The distance between the two villages is measured to be 8cm on a map.If the woman takes 3 minutes to travel from one village to another,find the scale of the map.
(5) On a map with a scale 2cm:9km,the distance between cityA and cityB is 5cm.
(a) Find the actual distance between cityA and cityB.
(b) Johnny takes 50 minutes to ride a bicycle from cityA and cityB.Find his riding speed in km/h.
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回答 (2)
2012-01-31 7:33 am
✔ 最佳答案
1.////////////////////////////////////////////////////
Peter Ann Bro
1 : 2
3 : 2
(8 stamps)
<12s>
<12+8 = 20s>
<10s> : <20s>
30 stamps @ beginning
//////////////////////////////////////////////////
2.
////////////////////////////////////////////////
<Collin> 45 w/min
<Chris> 45 / (9/10) = 50 w/min(a) (45+50)x5 =475words (b) 475 / 2 = 237.5......
237.5/45 = 5.278
237.5/50 = 4.75
Collin : Chris = 5.278/4.75 =1.11 : 1
////////////////////////////////////////////////////////
3.
/////////////////////////////////////////////
(1:25000) > (1: 75000)
3 : 1
////////////////////////////////////////////
4.
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24 / 60 x 3 = 1.2 km1.2 x 1000 x 100 = 120000 cm8 : 120000 = 1 : 15000
/////////////////////////////////
5.
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2cm : 9km = 1cm = 4.5km(a) Distance = 5 x 4.5 = 22.5km (b) 22.5 / 50 x 60 =27km/h
////////////////////////////////////
參考: 我既神算
2012-01-31 1:08 pm
(1)
Ratio: Peter: Ann 1:2 i.e. 3:6
Ratio: Ann: Her brother 3:2 i.e. 6:4
Ratio: Peter: Ann: Her brother 3:6:4
Total 3+6+4 = 13
Peter gets 3/13 of total ; Ann gets 6/13 of total ; Her brother gets 4/13 of total
Her brother gets 8 stamps. That means 8 stamps is 4/13 of total
The total = 8/4 (13) = 26
There are 26 stamps in the beginning.
(2)
(a) Collins typing speed = 45 words/min
Christ typing speed = 45 words/min /9 x 10 = 50 words/min
Number of words collin types = 45 w/min x 5 min = 225 words
Number of words Chris types = 50 w/min x 5 min = 250 words
Total number of words = 225 words + 250 words = 475 words
The entire document contains 475 words
(b) Since speed x time = total number of words typed
time is inversely proportional to speed
Ratio: Typing speed of Collin : Typing speed of Chris 9:10
Ratio of Time taken by Collin to time taken by Chris 10 : 9
Check: Assume the document contains 450 words
Time taken by Collin = 450 w/45w/min = 10 min
Time taken by Chris = 450 w/50w/min = 9 min
Ratio of Collin’s time to Chris’ time 10:9
(3) The actual distance 25000A cm or 75000B cm
25000A = 75000B
A/B = 75000/25000 = 3/1
Ratio of A to B is 3 to 1
(4)
The actual distance = 24 km//60min x 3 min = 1.2 km = 1.2 x 100000 cm = 120000 cm
8 cm represents 120000 cm , 1 cm represent 120000/8 = 15000 cm
The scale of the map is 1:15000
(5)
(a) 9km/ 2 cm = 4.5 km per cm, 1 cm represents 4.5 km
5 cm = 4.5 km/cm x 5 cm = 22.5 km
Distance between city A and city B is 22.5 km
(b) speed = distance/ time
distance = 22.5 km
time = 50/60 h
speed = 22.5 km /(50/60)h = 27 km/h
Johnny's riding speed is 27 km/h
Ratio: Peter: Ann 1:2 i.e. 3:6
Ratio: Ann: Her brother 3:2 i.e. 6:4
Ratio: Peter: Ann: Her brother 3:6:4
Total 3+6+4 = 13
Peter gets 3/13 of total ; Ann gets 6/13 of total ; Her brother gets 4/13 of total
Her brother gets 8 stamps. That means 8 stamps is 4/13 of total
The total = 8/4 (13) = 26
There are 26 stamps in the beginning.
(2)
(a) Collins typing speed = 45 words/min
Christ typing speed = 45 words/min /9 x 10 = 50 words/min
Number of words collin types = 45 w/min x 5 min = 225 words
Number of words Chris types = 50 w/min x 5 min = 250 words
Total number of words = 225 words + 250 words = 475 words
The entire document contains 475 words
(b) Since speed x time = total number of words typed
time is inversely proportional to speed
Ratio: Typing speed of Collin : Typing speed of Chris 9:10
Ratio of Time taken by Collin to time taken by Chris 10 : 9
Check: Assume the document contains 450 words
Time taken by Collin = 450 w/45w/min = 10 min
Time taken by Chris = 450 w/50w/min = 9 min
Ratio of Collin’s time to Chris’ time 10:9
(3) The actual distance 25000A cm or 75000B cm
25000A = 75000B
A/B = 75000/25000 = 3/1
Ratio of A to B is 3 to 1
(4)
The actual distance = 24 km//60min x 3 min = 1.2 km = 1.2 x 100000 cm = 120000 cm
8 cm represents 120000 cm , 1 cm represent 120000/8 = 15000 cm
The scale of the map is 1:15000
(5)
(a) 9km/ 2 cm = 4.5 km per cm, 1 cm represents 4.5 km
5 cm = 4.5 km/cm x 5 cm = 22.5 km
Distance between city A and city B is 22.5 km
(b) speed = distance/ time
distance = 22.5 km
time = 50/60 h
speed = 22.5 km /(50/60)h = 27 km/h
Johnny's riding speed is 27 km/h
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