maths
2007-03-07 4:35 am
A factory produces 800 cars in N days . If the factory produces 10 more cars in each day , then it will take four days less to produce 800 cars . Find the value of N
回答 (2)
2007-03-07 4:49 am
✔ 最佳答案
Let x be the number of cars produced in one day.800 = Nx -- (1)
800 = (N-4)(x+10) -- (2)
From (1), x = 800/N.
Sub x = 800/N into (2)
800 = (N-4)(800/N+10)
= 800 - 3200/N + 10N - 40
40 = 10N - 3200/N
40N = 10N^2 - 3200
0 = 10N^2 - 40N - 3200
= N^2 - 4N - 320
= (N + 16)(N - 20)
N = -16 or N = 20
As N > 0, so, N = 20.
Therefore, N = 20.
2007-03-07 5:04 am
800/x = n
800/ (x+10) = n-4
800 = (n-4) (800/n +10)
800 = 800 + 10n - 3200/n -40
40 = 10n - 3200/n
10n2 -40n -3200 = 0
(n-20)(n+16)=0
n=20 days
800/ (x+10) = n-4
800 = (n-4) (800/n +10)
800 = 800 + 10n - 3200/n -40
40 = 10n - 3200/n
10n2 -40n -3200 = 0
(n-20)(n+16)=0
n=20 days
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