GMAT paper test 52

by **Guest** Mon Sep 17, 2007 2:56 pm

this is #14 on the GMAT paper test-

What is the least number of digits (including repetitions) needed to express 10^100 in decimal notation?

a) 4
b) 100
c) 101
d) 1000
e) 1001

where do I start? I think there is something about adding 1, so I'm narrowing my choices to c or e? any thoughts?

by **Guest** Mon Sep 17, 2007 4:52 pm

You are almost there. The answer is (C)

10^1 = 10(2 digits)
10^2 = 100(3 digits)
10^3 = 1000(4 digits)
10^100 --(100 0's + 1 digit for 1 = 101)

by **RonPurewal** Tue Sep 18, 2007 3:59 am

What's here is correct.

This is a PATTERN RECOGNITION problem. If you look at the Guest post (the one starting with "You are almost there"), you'll notice the pattern: it takes N+1 digits to write out 10^N in decimal notation.

To me, the weirdest thing about this problem is the word "least," since the decimal notation for any given integer is unique. (Unless they're trying to exclude possibilities like 10^3 = 1000.0000000000000 with seventeen digits)