GMAT 数学题（16）

sdcar2010 · 发表于 2011-2-13 03:45:03

There are a group of triangular numbers. If A(n) is the nth number of this group, then A(n) = (n*(n+1))/2. n is an integer bigger than 0.

There are a group of square numbers. If Bn is the nth number of this group, then B(n) = n^2. n is an integer bigger than 0.

If A(n) + A(m) = B(p) while both A(n) and A(m) are smaller than 100, what is the the largest possible value for A(n)? Why?

A) 45
B) 55
C) 66
D) 78
E) 91

kazemi · 发表于 2011-2-13 04:30:45

推算过程太长，我应该不会算，直接从五个答案中按从大到小顺序代入验证

sdcar2010 · 发表于 2011-2-14 06:59:49

推算过程太长，我应该不会算，直接从五个答案中按从大到小顺序代入验证

-- by 会员 kazemi (2011/2/13 4:30:45)

All right. Here are the five choices:

A) 45
B) 55
C) 66
D) 78
E) 91

zoechancruz · 发表于 2011-2-14 07:40:01

答案选B么

kazemi · 发表于 2011-2-14 08:39:43

提示，看从E到A这些数*2都有哪些因子

sdcar2010 · 发表于 2011-2-14 11:17:55

答案选B么

-- by 会员 zoechancruz (2011/2/14 7:40:01)

Hmmmm.

45+55 = 100 does look convenient as an answer choice. But that would be too easy.

kazemi · 发表于 2011-2-14 11:50:53

Don't know what you're saying here...

I can tell 91*2=13*14

sdcar2010 · 发表于 2011-2-14 11:56:15

A(n) and A(m) is from:
A) 45
B) 55
C) 66
D) 78
E) 91

B(p) is from 100, 121, 144, etc.

A(n) + A(m) = B(p)

What is the biggest possible A(n)?

45 +55 =100 fulfills the requirement of the equation. But 55 is not the biggest possible answer.

kazemi · 发表于 2011-2-14 12:08:09

I thought u were on the wrong direction...

sdcar2010 · 发表于 2011-2-14 12:15:56

Another way to describe this problem is:

The sum of two triangular numbers is a square number. What is the biggest possible value for the triangular number smaller than 100?

A) 45
B) 55
C) 66
D) 78
E) 91

GMAT 数学题（16）

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