[討論] 請教2題數學
1. JULY ELECTRICIT USAGE FOR THE SMYTHE HOUSEHOLD
water heater 20%
light/small appliances 9%
large appliances 18%
air conditioner 53%
ELECTRICITY USED:800 kilowatt-hours
Q:The electricity used by the water heater was measured separately and its
cost per kilowatt-hour was one-half the cost per kilowatt-hour of the rest
of the electricity used. The cost of the electricity used by the water hea
ter was most nearly what fraction of the total cost of all the electricity
used?
<a>1/11
<b>1/9-------right answer
<c>1/8
<d>1/5
<e>it cannot be determined from the information given.
2. n/4 + r/8 = s/8 + t/6 , n,r,s and t are positive integers.
2n+r 跟 2s+t 誰比較大
答案是A
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