简单数学题但是我不会急

guo573874201 · 发表于 2011-9-3 06:30:32

1. What was the price at which a merchant sold a certain appliance?
(1)The merchant’s gross profit on the appliance was 20 percent of the price at which the merchant sold the appliance.
(2)The price at which the merchant sold the appliance was $50 more than the merchant’s cost of the appliance.答案C

2. C_(m,n) = m! / [(m-n)! n!] for nonnegative integers m and n, m ³ n.If C_(5,3) = C_(5,x) and x ¹ 3, what is the value of x? 答案是2
3. If w, x, y, and z are integers such that 1 < w < x < y < z and wxyz = 462, then z =? 答案是11
4. On a certain transatlantic crossing, 20 percent of a ship’s passengers held round-trip tickets and also took their cars abroad the ship.If 60 percent of the passengers with round-trip tickets did not take their cars abroad the ship, what percent of the ship’s passengers held round-trip tickets?答案50%
5. The value of (9´10⁷)(9´10⁸) is closest to which of the following?答案是10的17次方

请讲解具体的过程拜托了！

wyw1018 · 发表于 2011-9-3 08:07:21

2、有定理C(m,n)=C(m,m-n)
3、462=2×3×7×11因此z=11
4、设总人数x，有round-trip tickets人数为y 根据题意0.2x=（1-0.6）y-->y/x=0.5
5、式子=81×10^15=0.81×10^17

wyw1018 · 发表于 2011-9-3 08:12:02

1、设成本为x 售价为y
条件1得 y-x=0.2y 不充分
条件2得y-50=x 不充分
两个条件一起可解

soulkitchen · 发表于 2011-9-3 08:40:15

3. If w, x, y, and z are integers such that 1 < w < x < y < z and wxyz = 462, then z =?

分解462的质因数, 得462=2*3*7*11, 那么w=2, x=3, y=7, z=11

简单数学题但是我不会急

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简单数学题但是我不会急