请较几道不解之题

XIAOSHAONIAN

请教大侠

DS:

What is the remainder when the positive integer n is divided by the positive integer K, where K>1

1) n=(k+1)^3  ;    2)  K=5

Answer : A   ....why ?

Is the integer N odd ?

1) N is divisible by 3    2) 2N is divisible by twice as many positive integer as N

Answer: B.... why?

If  -2x>3y is x negative ?

1) y>0    2) 2x+5y-20=0    

Answer: D...... why 2) is also OK?

PS:   How many different 6-letter sequences are there that consist of 1 A, 2 B, 3 C ?

a.)6;  b) 60;  c)360;  d) 720       Answer: B ......

mingzhu11

QUOTE:

DS:

What is the remainder when the positive integer n is divided by the positive integer K, where K>1

1) n=(k+1)^3  ;    2)  K=5

Answer : A   ....why ?

n=(k+1)^3

n=k^3+3k^2+3k+1

QUOTE:

If  -2x>3y is x negative ?

1) y>0    2) 2x+5y-20=0    

Answer: D...... why 2) is also OK?

2x+5y=20 => y=4-0.4x => 3y=12-1.2x

-2x>12-1.2x => -0.8x>12

QUOTE:

PS:   How many different 6-letter sequences are there that consist of 1 A, 2 B, 3 C ?

a.)6;  b) 60;  c)360;  d) 720       Answer: B ......

P(6,6)/(P(2,2)*P(3,3))

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