我有3絛數唔識,唔該教下我.(10分)
1) 3y/2 + p-7y/2 =W
y=?
2) John's saving is$300 more than his sister"s.After giving$450 from his savings to his sister,John becomes 2/5 of his sister's. .How much saving do they have altogether?
3)A car uses 1/4 of its petrol in the first day of a trip, and 1/5 of the rest on the second day.What was the original amount of petrol in the car if there is 6L of petrol left in the tank?
Maths
2006-11-25 5:29 pm
回答 (5)
2006-11-25 5:53 pm
✔ 最佳答案
1)3y/2 - (p-7y)/2 = w
3y - (p-7y) = 2w
10y = 2w+p
y = (2w+p)/10
2)
Let John and his sister's money be x and y,
x-300 = y ---(1)
(x-450) = (2/5) x (y+450) ---(2)
Solve the above eqt and get x=850, y=550
3)
Let the org. volumn be x,
x (1- 3/4) (1- 1/5) = 6
x = 10L
2006-11-25 5:52 pm
1) 3y/2 + p -7y/2 = W
(3y-7y)/2 +p = W
(-4y)/2 +p=W
p-2y = W
p - W = 2y
y = (p-W)/2
2) Let the saving of John's sister be x, then john's saving is x + 300
John's saving - 450 = 2/5 his sister's saving
(x + 300) - 450 = 2/5 x
x - 2/5x = 450 - 300
3/5x = 150
x = 150 x 5 / 3
x = 250
John's sister's saving is 250 and john's saving is (250 + 450) = 700
3. Let the original amount of petrol be x. after the first day, there is 3/4 x left
(3/4x) (1- 1/5) = 6
(3/4x)(4/5) = 6
x = 6 (5/4)(4/3)
= 10
(3y-7y)/2 +p = W
(-4y)/2 +p=W
p-2y = W
p - W = 2y
y = (p-W)/2
2) Let the saving of John's sister be x, then john's saving is x + 300
John's saving - 450 = 2/5 his sister's saving
(x + 300) - 450 = 2/5 x
x - 2/5x = 450 - 300
3/5x = 150
x = 150 x 5 / 3
x = 250
John's sister's saving is 250 and john's saving is (250 + 450) = 700
3. Let the original amount of petrol be x. after the first day, there is 3/4 x left
(3/4x) (1- 1/5) = 6
(3/4x)(4/5) = 6
x = 6 (5/4)(4/3)
= 10
2006-11-25 5:46 pm
1) ans: y=(p-w)/2
收錄日期: 2021-04-12 19:31:45
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