有两道数学题请教大家，谢谢啦

songchangwen

Q23:

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?

A.33

%

B.40%

C.50%

D.60%

E.66

%
Q27:

When the positive integer n is divided by 13, the remainder is 4.What is the remainder when 2n – 3 is divided by 13 ?

A.1

B.3

C.5

D.7

E.9

sdcar2010

Let's say there are 100 passengers in total. According to the stimulus, 20 of them have round-trip tickets and their cars. Then from the condition that "60 percent of the passengers with round-trip tickets did not take their cars", you know that 40% of the passengers with round-trip tickets DID take their cars.

So the number of round-trip ticket holders = 20/40% = 50

50/100 = 50%

sdcar2010

Pick the number of 17, which satisfies the first condition.  2 x 17 -3 = 31.  Then 31/13, the remainder is 5.