GMAT 数学题（16）

lpchen0613 · 发表于 2011-2-14 15:40:38

答案选E，2A(n)=13*（13+1），所以A(n)=91，
2 A(m)=12*（12+1）所以 A(m)=78
B(p)=13^2=169
A(n)+A(m)=91+78=169= B(p)
这样对吧，自己做的，大家看看，仅供参考参考

sdcar2010 · 发表于 2011-2-14 21:30:31

LS is right. The answer is E, 91.

sdcar2010 · 发表于 2011-2-14 21:37:25

The key is to realize that the sum of any consecutive A(n) and A(n+1) is a square number!!!

55+66 = 121
66+78 = 144
78+91 = 169
...

neverlandlin · 发表于 2011-2-14 21:50:00

弱弱问一句，什么叫triangular numbers ？

sdcar2010 · 发表于 2011-2-15 08:00:36

弱弱问一句，什么叫triangular numbers ？

-- by 会员 neverlandlin (2011/2/14 21:50:00)

http://en.wikipedia.org/wiki/Triangular_number

A triangular number is the number of dots in an equilateral triangle uniformly filled with dots. For example, three dots can be arranged in a triangle; thus three is a triangle number. The nth triangle number is the number of dots in a triangle with n dots on a side.
A triangle number is, equivalently, the sum of the nnatural numbers from 1 to n.

GMAT 数学题（16）

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