標標 asked in 科學及數學數學 · 6 years ago

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1.Mr.chung 's age is 8 times his daughter's age this year. 12 years later , the sum of their age will be 87. how old is Mr.chung now?

2.A father 's age is 3 times his son's age 7 years ago.if the sum of their age is 70 now. Find their ages 7 years ago.

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  • 6 years ago
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    1. Mr. Chung 's age is 8 times his daughter's age this year. 12 years later , the sum of their age will be 87. how old is Mr. Chung now?

    Let x be the age of Mr. Chung now.

    His daughter's age now is x/8.

    12 years later,

    (x + 12) + (x/8 + 12) = 87

    9x/8 + 24 = 87

    9x/8 = 63

    x/8 = 7

    x = 56

    Mr. Chung is 56 years old now.

    2. A father 's age is 3 times his son's age 7 years ago.if the sum of their age is 70 now. Find their ages 7 years ago.

    Let x be the son's age 7 years ago.

    The father's age 7 years ago is 3x.

    Now, the ages of the son and the father are respectively x+7 and 3x+7.

    (x + 7) + (3x + 7) = 70

    4x + 14 = 70

    4x = 56

    x = 14

    Therefore, 7 years ago, the son's age was 14 and the father's age was 14*3 = 42.

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