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from.1 (maths)

發問:

1.Andy is fourteen years older than Nicholas.Andys age was three times that of Nicholas sixteen years ago.Find the present age of Nicholas. 2.A bag contains 200 coins.The total value of these coins is＄400.If there are m ＄5 coins and all of others are 20￠ coins,find a).the value of m. b)the numberof 20￠ coins.

 

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最佳解答:

1.Andy is fourteen years older than Nicholas. Andy’s age was three times that of Nicholas sixteen years ago. Find the present age of Nicholas. Assume Andy is x years old. Nicholas is x – 14 years old. Six year ago Andy is x – 6 years old. Nicholas is x – 20 years old. x – 6 = 3(x – 20) x – 6 = 3x – 60 54 = 2x x = 27 2.A bag contains 200 coins. The total value of these coins is＄400.If there are m ＄5 coins and all of others are 20￠ coins, find a).the value of m. 5m + 0.2(200 – m) = 400 5m + 40 – 0.2m = 400 4.8m = 360 m = 75 b)the number of 20￠ coins 200 – 75 = 125 There are 125 20 coins

其他解答:

1. Let x be the present age of Nicholas. Andy' s present age is x +14 Sixteen years ago, Nicholas' s age was x - 16, Andy' s age was (x + 14) - 16 Andy' s age was three times that of Nichola' s sixteen years ago. (x + 14) - 16 = 3 (x - 16) x - 2 = 3x - 48 3x - x = 48 - 2 2x = 46 x = 23 ∴ Nichola' s present age is 23 2. Let m be the number of $5 coins, the number of 20￠ coins = 200 - m The total value of these coins is＄400. 5m + 0.2 (200 - m) = 400 5m + 40 - 0.2m = 400 4.8m = 400 - 40 4.8m = 360 ∴ m = 75 The number of 20￠ coins = 200 - m = 200 - 75 = 125D1B39E804036C6BD

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