maths(inequalities)
2007-12-08 3:54 am
Peter has 40 dollars and he want to buy 30 ball pens and pencils. Ball pen is 2.5 dollars each and pencil is 0.8 dollar. Find the minimum number of pencil he should buy.
回答 (1)
2007-12-08 5:51 am
✔ 最佳答案
Let x be the number of pensLet y be the number of pencils
2.5x + 0.8y <= 40 ----------------- (1)
x + y = 30 -----------------------------(2)
From (2), x = 30 - y ----------------(3)
Sub (3) into (1):
25 (30 - y) + 8y <= 400
750 - 25y + 8y <= 400
750 - 17y <= 400
-17y <= -350
y >= 350/17
y>= 20+10/17
The minimum number of pencil he should buy is 21.
參考: me
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