數學.............20分

yoyo08hk2001

2007-07-21 6:19 am

請問以下的數學題目,中文是甚麼和算式又是甚麼??

1.What is the sum of the next 3 even numbers starting from 21?

2.Raymond spent 75分之13 of his money on a book and spent 31分之21 of the
remainder on a watch.He then had $120 left.How much money did he have at first?

3.4 times u(代數) and then take 10 from the product

4.Subtract the product of v(代數) and w(代數) from 20

5.Given 2 numbers x(代數) and 198.If the H.C.F. is 18 and L.C.M. is1386,find x(代數)

回答 (1)

abaform

2007-07-21 8:05 am

✔ 最佳答案

1. 由21開始, 之後３個雙數的和是什麼?
答: 之後３個雙數是22, 24 及26, 總和是 22 + 24 + 26 = 72

2. Raymond 用 75分之13的錢買了一本書
用剩下的31分之21買手錶, 之後餘下$120, 問他原本有多少錢?
答: 設他原有 $x, 方程式是
x * (1 - 13/75) * (1 - 21/31) = 120
x * 62/75 * 10/31 = 120
x * 4/15 = 120
x = 120 * 15 / 4 = 450
他原有$450

3. 問題不清楚, 表達式是 4u - 10
4. 問題不清楚, 表達式是 20 - wv
5. 先把198, 18及1386寫成質數相乘
198 = 2 * 3 * 3 * 11
HCF(x, 198) = 18 = 2 * 3 * 3
LCM(x, 198) = 1386 = 2 * 3 * 3 * 7 * 11
要得HCF = 18, x 必能拆成 2 * 3 * 3 = 18 為當中部分
LCM中, 198不能被7除盡，但1386可以，所以 x 一定是7的倍數
綜合2點，x = 2 * 3 * 3 * 7 = 18 * 7 = 126

參考: 自己

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