XYZ asked in 科學及數學數學 · 9 years ago

4條F.1數學問題(列式解答)

1(正負數). 5(4-r)-2(3r+10)=22

2(方程) .If the sum of three consecutive integers is -21,Find the largest integer.

3(方程). The weight of a cat is 0.3kg more than 12 times that of a rat , while the weight of a dog is 0.2 kg less than 14 times that of the rat. If the weight of the cat and the dog are the same,

(a) what weight in kg is the rat ?

(b) what weight in kg is the cat?

4.(方程)In an exhibition , the prices of an adult ticket and a student ticket are $75 and $30 respctively. If on a day 490 tickets are sold altogether and then total incomes is $30450,find

(a)the number of adult tickets sold and the amount received

(b)the number of student tickets sold and the amount received

2 Answers

Rating
  • 9 years ago
    Favorite Answer

    1.

    5(4-r)-2(3r+10)=22

    20-5r-6r-20=22

    -11r=22

    r=-1/2

    2.

    let the largest integer be x

    (x-2)+(x-1)+x=-21

    3x-3=-21

    3x=-18

    x=-6

    therefore, the largest integer is -6

    3(a)

    let the weight of the rat be y kg

    12y+0.3=14y-0.2

    0.5=2y

    y=0.25

    therefore,the weight of the rat is 0.25kg

    (b)

    12*0.25+0.3

    =3.3kg

    4.(a)

    let the number of adult tickets and student tickets sold be x and y respectively

    x+y=490...(1)

    75x+30y=30450..(2)

    from (1),

    y=490-x...(3)

    sub (3) into (2),

    75x+30(490-x)=30450

    75x+14700-30x=30450

    45x=15750

    x=350

    therefore,the number of adult tickets sold is 350.

    350/75

    =$26250

    therefore, the amount received by selling adult tickets is $26250

    (b)

    sub x=350 into (1)

    350+y=490

    y=140

    therefore,the number of student tickets sold is 140.

    140*30

    =$4200

    therefore, the amount received by selling student tickets is $4200

    2011-10-30 12:49:55 補充:

    1.

    5(4-r)-2(3r+10)=22

    20-5r-6r-20=22

    -11r=22

    r=-2

    Source(s): me
  • 9 years ago

    1. 20-5r-(6r+20)=22

    -r =22

    r=-22

    2. a+1+a+2+a+3=-21

    3a+ 6=-21

    3a = -27

    a = -9

    so the largest integer is -9 +3 = -6

    Source(s): me
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