3條f.2升f.3數學(率和比)(7點)!!

1.
100美元
= 100美元 * (7.78港元/1美元) *(1歐元/11.2港元)
= 69歐元 (準確至最接近的歐元)


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2.
(a)
(3a + 2b) : (a + 6b) = 2 : 1
2(a + 6b) = 3a + 2b
2a + 12b = 3a + 2b
a = 10b
a/b = 10
a : b = 10 : 1

(b)
a : b = 10 : 1
設 a = 10k 及 b = k

(2a + b) : (3a - b)
= (2*10k + k) : (3*10k - k)
= 21k : 29k
= 21 : 29