Here are two GMAT Prep questions that are fairly easy, but

Question

Here are two GMAT Prep questions that are fairly easy, but my knowledge on the rules of exponents is a bit shaky so I'm looking for some help. 

Which of the following equals 2^5 + 2^5 + 3^5 + 3^5 + 3^5?

5^6
13^5
2^6 + 3^6
2^7 + 3^8
4^5 + 9^5


Second question,

(10^8 - 10^2) / (10^7 - 10^3) =

1
10
10^2
10^3
10^4

Thanks in advance,

Himalayan · Answer

2^6 + 3^6

is the question (10^8 - 10^2) / (10^7 - 10^3) = ?

then, it should 

B. 10.

but it is approx...........

bz9 · Answer

I edited the question for clarity. 

Thanks,

bz9 · Answer

For the first question, do you just work the problem and go from there or is there a shorcut for adding and subtracting exponents?


For the second question, same thing do just work the problem? 

i.e. 100000000 - 100 / 10000000 - 1000

empanado · Answer

Yes, it'd be good to know if there is a quicker way to do it than to just work the problem by "hand".

mbagal1 · Answer

1. (2^5 + 2^5 )+ (3^5 + 3^5 + 3^5)
= 2*(2^5) + 3*(3^5)
=2^6+3^6

2. 10^2(10^6-1)/10^3(10^4-1)
= 10^6 - 1 is approx 10^6
10^4-1 is approx 10^4

=> 10^6/(10^4* 10) = 10 (approx)

empanado · Answer

Why did you multiply 10^4* 10?? 

Thanks!

mbagal1 · Answer

Because 10^2/10^3 = 1/10.

bz9 · Answer

Thanks Hsampath,

Perfectly clear now and the OA are B & C.

kyatin · Answer

YOu really mean C & B , right

bz9 · Answer

Good spot kyatin.

OA is C & B

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