看不懂的题目:(

deedeexoxo · 发表于 2008-6-8 12:58:00

求助！！

If 10⁵⁰ – 74 is written as an integer in base 10 notation, what is the sum of the digits in that integer?

A. 424

B. 433

C. 440

D. 449

E. 467

I got C... 2+6 + ４８x9. but the answer key says its b...

[此贴子已经被作者于2008-6-8 13:12:49编辑过]

deedeexoxo · 发表于 2008-6-8 13:14:00

哦就是 C...我看错了。不好意思

bth · 发表于 2008-6-8 14:39:00

the resultant number will have 48 9s and then 2 in tens and 6 in units place
adding them gives 440

bth · 发表于 2008-6-8 14:42:00

This problem can be solved in the following way:

10 has power 50 means after 1 there will be 50 zeroes.

1

Zero no. 1

2

3

4,5, ………..48

49 and 50

1

0

00000000……

00

74

9

99999999……

26

There are 50 zeroes after 1. So, (50 – 2) or 48 9’s are remaining after deducting 74 + the two digits are 26.

So, the result will be = (9 ×48)+2+6 = 432+8=440.

所属分类: GMAT考试