[計量] 幾題數學求解

[grassroots (阿根)]

1. For a nonnegative interger n, if the remainder is 1 when 2^n is divided by
   3, then which of the following must be true?(多選)
   A. n is greater than 0
   B. 3^n=(-3)^n
   C. 根號2^n is an integer

2. If y is inversely proportional to x and y is 15 when x=5, what is the
   value of y when x=25?
   我是算y:x=15:5=75:25 故y=75.
   但答案是y=3, 請問是我哪邊理解錯了？

3. {a,b} represents the remainder when a is divided by b.
   c and d are positive intergers with c<d.(比大小)
   A: {c,d}
   B: {d,c}

4. If p and q are primes greater than 2, which of he following must be true?
   (多選)
   A. p+q is even
   B. pq is odd
   C. p^2+q^2 is even
   D. 4p-q is even
   E. p/2+q/2 is even

5. 這題我真的有看沒有懂...
   Pat drove from his home to school at 60 miles per hour. Returning over the
   same route, there was a lof of traffic, and he was only able to drive at
   40 miles per hour. If the return trip took 1 hour longer, how many miles
   did he drive for the round trip? (填空)

先謝過板上高手了

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推 wenwen0616  : 1.B,C  2.題目說成反比 15*5=3*25  3.A>B  4.ABC  5
→ wenwen0616  : .80miles
推 Jincheng56  : 第四題,大於二的質數一定是奇數
→ Jincheng56  : a)奇加奇是偶
→ Jincheng56  : b)奇乘奇是奇
→ Jincheng56  : c)奇平方還是奇，同a
→ Jincheng56  : d)4奇=偶，偶加奇=奇
→ Jincheng56  : e)帶入13和17是奇
推 bbbb0829    : 第二題題目是給反比 你答成"成正比"的答案了
→ bbbb0829    : 反比的式子是 Y=常數/X -> XY=常數 這樣就可以解了
推 bbbb0829    : 第三題是A D>C 所以 D/C = 值...小於C的數值
→ bbbb0829    : 而 C/D = 0....C  答案就出來了
推 bbbb0829    : 第五題 先假設去程所花時間為X小時,則回程為X+1
→ bbbb0829    : 得到算式 X*60 = (X+1)*40 -> X = 2 小時
→ bbbb0829    : 2小時乘以60 miles/H 得到單趟路程為120miles
→ bbbb0829    : 再*2 就可以得到來回總路程為240 miles