问大家几道GWD的数学题 谢谢大家

renaultboy

如题 几道GWD数学题 1楼2道

GWD1 (18)

For any positive integer n, the sum of the first n positive integers equals [n(n+1)]/2. what is the sum all of the even integers between 99 and 301?

A 10100

B 20200

C 22650

D 40200

E 45150   答案 B



GWD2 (18)

On a certain transatlantic crossing, 20percent 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 1/3%

B 40%

C 50%

D 60%

E 66 2/3%   答案 C


GWD3 (14)

How many seconds will it take for a car that is traveling at a constant rate of 45 miles per hour to travel a distance of 22 yards? (1mile=1160 yards)

A 8

B 9

C 10

D 11

E 12   答案 C     这道题算了好多次 为什么都是1.5？



GWD5 (19)

In a survey of 200 college graduates, 30 percent said they had received student loans during their college careers, and 40 percent said they had received scholarships. What percent of those surveyed said that they had received neither student loans nor scholarships during their college careers?

(1)    25 percent of those surveyed said that they had received scholarship but no loans

(2)    50 percent of those surveyed who said that they had received loans said that they had received scholarships

答案 D   一点也算不出来

tobytracy

GWD1 (18)

For any positive integer n, the sum of the first n positive integers equals [n(n+1)]/2. what is the sum all of the even integers between 99 and 301?

A 10100

B 20200

C 22650

D 40200

E 45150   答案 B
这题题目问的是偶数项，所以把他堪称是首相为100末项是300，公差为2的等差数列求和就可以啦

renaultboy

我好像理解了题的意思了 谢谢

但是为什么用等差数列我总是算的不对呢

Sn=na1+n(n-1)d/2 这个不是等差数列公式么

na1=100

d=2

n=100

得数差的好远 谢谢指点