分數大放送 Maths

Ka Ho

2012-12-12 5:59 am

點後/有括號是題目

1 Oscar and Peter are now 32 and 28 years old respectively.
1(a)Find the ratio of Oscar age to Peter age 4 years ago.
1(b)Find the ratio of Oscar age to Peter age 8 years later.

2 A shop sold apples,oranges and pears.In a day,360 fruits are sold, where the ratio of the number of apples to that of oranges is 2:3,and the ratio of the number of apples to that of pears is 4:5.
2(a) Find the ratio of the number of apples sold to that of oranges to that of pears.
2(b)Find the number of apples,oranges and pears sold respectively.

3 Amy and Billy have 75 and 25 marbles respectively.If Amy gives some marbles to Billy, the ratio of the number of Amy marble to that of Billy becomes 3:7. 3.Find the number of marbles Amy gives Billy.

回答 (1)

andrew

2012-12-12 6:39 am

✔ 最佳答案

1.
(a)
4 years ago, (Oscar age) : (Peter age)
= (32 - 4) : (28 - 4)
= 28 : 24
= 7 : 6

(b)
8 years later, (Oscar age) : (Peter age)
= (32 + 8) : (28 + 8)
= 40 : 36
= 10 : 9

=====
2.
(a)
Let a, r and p be the numbers of apples, oranges and pears respectively.

a : r = 2 : 3 = 4 : 6
a : p = 4 : 5

Hence, a : r : p = 4 : 6 : 5

(Number of apples) : (Number of pears)
= 6 : 5

(b)
Number of apples
= 360 x [4 / (4 + 6 + 5)]
= 96

Number of orange
= 360 x [6 / (4 + 6 + 5)]
= 144

Number of pears
= 360 x [5/(4 + 6 + 5)]
= 120

=====
3.
Let n be the number of marbles that Amy gives to Billy.

(75 - n) : (25 + n) = 3 : 7
3(25 + n) = 7(75 - n)
75 + 3n = 525 - 7n
10n = 450
n = 45

Hence, the number of marbles that Amy give to Billy = 45

參考: andrew

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