请教涛涛GWD1-14

dreadpower

Q14:
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. 

E. 

467

answer:c

看不懂这道题的题意,哪位好心人能指点迷津?

mikejia

10^50

10的50次方减去74, 这个数长的这个样子99999999999999999999999......9999926.

每位数的和就是 9*48 +2+6= 440

dreadpower

为什么要出现"in base 10 notation"

式子等于48*9+2+6=440,但为什么要出现"in base 10 notation"呢?

windfalls

同问in base 10 notation是什么意思？

Thanks.

luoye1

maybe you remember the "base 2 notation" in computer

any integer can be represented in "base 10 notation" as:

n=a0*10^0+a1*10^1+a2*10^2+...+an*10^n+...

and in "base 2 notation" as:

n=b0*2^0+b1*2^1+b2*2^2+...+bn*2^n+...