If 10^50 – 74 is written as an integer in base 10 notation what is the

Question

If  10^{50} – 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

Bunuel · Accepted Answer

If (10^50) – 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

Based 10 notation, or decimal notation, is just a way of writing a number using 10 digits: 1, 2, 3, 4, 5, 6, 7, 8, and 0 (usual way), in contrast, for example, to binary numeral system (base-2 number system) notation.

10^{50}  has 51 digits: 1 followed by 50 zeros;
 10^{50}-74  has 50 digits: 48 9's and 26 in the end;

So, the sum of the digits of  10^{50}-74  equals to 48*9+2+6=440.

Answer: C.

Hope it helps.

nsp007 · Answer

C. 440

10^x - 74 --> last 2 digits are always 2, 6.

10^2 - 74 = 26

10^3 - 74 = 926

10^4 - 74 = 9926 and so on....

If x > 1,
the sum of the digits --> (x-2) * 9 + 2 + 6. hence, (50-2) * 9 + 8 --> 440.

Bunuel · Answer

10^{50}  has 51 digits (1 followed by 50 zeros).  10^{50}-74  has 50 digits: last 2 digits are 2 and 6 (26) and first 48 digits are 9's.

Like 1,000-74=926.

So the sum of the digits is  9*48+2+6=440 .

Answer: C.

BrentGMATPrepNow · Answer

One approach is to look for a pattern...
10^3 - 74 = 1,000 - 74 =  9 26 (1  nine )
10^4 - 74 = 10,000 - 74 =  99 26 (2  nines )
10^5 - 74 = 100,000 - 74 =  999 26 (3  nines )
10^6 - 74 = 1,000,000 - 74 =  9999 26 (4  nines )
.
.
.
In general, we can see that 10^n - 74 will feature n-2  9 's followed by 26

So, 10^50 - 74 will feature 48  9 's followed by 26
This means the sum of its digits = 48( 9 ) + 2 + 6 = 432 + 2 + 6 =  440 \

Answer: C

KillerSquirrel · Answer

solving for easier numbers ---> 10^3 and 74

(10^4) - 74 =

(10^4) - 10*7.4 =

10*[(10^3) - 7.4] =

10*[10^3 - 7.4] = 992.6*10 = 9926 = 9*2+2+6 = 26

Note that 10^4 will yield two nines a six and a two.

so solving for 10^50 and 74 will give 48 nines a six and a two:

10*[10^49 - 7.4] = 9*48+2+6 = 440

the answer is (C)

:-D

PTK · Answer

C. 440 
another approach is: 
We know that 10^50 is ending 00, so 10^50-74=9....9926 
total number of digits in 10^50-74 is 50, or 48 digits of 9 and two digits 2 and 6. 
answer choice is 48*9+8=440

plugging numbers:
let represent the sum of the digits in that integer as Y, with the reminder 8, we can represent it in form Y=X*9+8, where X number of digits in 10^50-74 and 8=2+6.

Start with C and than move to B or D.

B. 433=X*9+1, X=48
C. 440=X*9+8, X=48 -  correct as we have the reminder 8 and 48 number of digits (50-2), 2 digits are 26.  
D. 449=X*9+8, X=49

Personally, I like NSP007's approach. My approaches are easy to comprehend.

ygdrasil24 · Answer

10^1 = 10
10^2 - 74 = 026
10^3 - 74 = 926
10^4 - 74 = 9926

Basically for 10^n , its 9999....(n-2)26.

So for 10^50-74, it is 99999....4826

48times9 + 2+6 = 440.

Lobro · Answer

I don't understand why in the question it is mentioned "in base 10 notation"

Maybe its because English is not my mother tongue but that instruction really confused me. I thought I was looking for a number like "ten to the power of something".

Bunuel · Answer

Based 10 notation, or decimal notation, is just a way of writing a number using 10 digits: 1, 2, 3, 4, 5, 6, 7, 8, and 0 (usual way), in contrast, for example, to binary numeral system (base-2 number system) notation. Similar questions to practice: the-sum-of-the-digits-of-64-279-what-is-the-141460.html the-sum-of-all-the-digits-of-the-positive-integer-q-is-equal-126388.html 10-25-560-is-divisible-by-all-of-the-following-except-126300.html if-10-50-74-is-written-as-an-integer-in-base-10-notation-51062.html Hope this helps.

PareshGmat · Answer

100 - 74 = 26

The last 2 digits of the term would be 26; all else would be 9

99999999......26

Important rule:

Sum of ANY NUMBER added to 9 would give the SAME value of itself

For example; Consider number = 13

Sum of digits = 1+3 = 4

Adding 9 to 13 = 22 = 2+2 = 4

So the sum would always remain the same;

Back to our problem

99999999......26 = The sum of this number will add up to 2+6 = 8

From the options available, A & B can be discarded

9x1 =  9 
9x2= 1 8 
9x3= 2 7 
9x4= 3 6 
9x5= 4 5 
9x6= 5 4 
9x7= 6 3 
9x8= 7 2    ........................................ 48th time  
9x9= 8 1 
9x10=9 0

99999999......26

10^{50}- 74  means 9 would be repeated 48 times; so last digit would be 2

Now we have 2+2+6 = 10 (Last digit is 0)

Only option C best fits = 440

Answer = C

dave13 · Answer

generis can you please explain ?

i dont understand how after 10^{50}-74 we have 50 digits

And how we get "last 2 digits are 2 and 6 (26) and first 48 digits are 9's"

generis · Answer

dave13 , I've seen you use patterns. Good instinct. Use a pattern. (I think you missed the "1,000" pattern above.) In other words, when exponents are huge, we can replicate the question with exponents that are manageable. Make the powers of 10 smaller and test a few. First we have to figure out what the digits ARE. That's just subtraction. Start with 100. (You could start with 1,000, which would be a little more accurate. 1,000 - 74 = 926. There is a 9. But, see below, 26 is always there.) Given (100-74), what is the sum of the digits?* 100-74 = 26. Sum of the digits? (2+6)=8 How many digits in the answer? TWO. You wrote: "i dont understand how after 10^{50}-74 we have 50 digits" The exponent, 50, gives us a clue, but we will not see that clue until after we go further with the earlier pattern. 100 = 10 ^2 . How many digits in 10^2 -74? TWO digits in the answer, 26 The exponent is a clue only. Simple subtraction, with a few examples will tell us how many digits. So let's go higher by powers of 10: 10 ^3 = 1,000 10 ^4 = 10,000 10 ^5 = 100,000 Subtract 74 from each one. (Writing on paper really shows the pattern. Formatting here is hard): (1,000 - 76) = 9 26 (10,000-76) = 9,9 26 100,000-76 = 99,9 26 (10^3 - 74) has THREE digits. One 9, and 26 (10^4 - 74) has FOUR digits. Two 9s, and 26 (10^5 - 74) has FIVE digits. Three 9s, and 26 1) We are getting the same number of digits as the exponent on 10 2) The last two digits will always be 26 3) We have to borrow to move the initial 1 to next place to the right and turn it into a 9. So: (1) there are repeated 9s, and (2) there are only 9s until 26. 4) How many 9s? Exactly TWO fewer than 10's exponent (because 2 and 6 "use up" two of the digits) Finally, SUM of the digits? Back to the pattern: Increasing powers of 10 (100, 1000, 10000) minus 74 produce an answer that has exactly the same number of digits as the exponent on the 10 has. 10 ^3 has 3 digits: a 9, a 2 and a 6. We need to know the number of digits so that we know how many 9s there are. 9 26 (10,000-76) = 9,9 26 100,000-76 = 99,9 26 10^3 - 74 = ((1*9)+26)=(9+26)=35 10^4-74 = ((2*9)+26)) =(18+26)=44 10^5-74= ((3*9)+26))=(27+26)=53 Try extrapolating from the pattern above to answer this question: What is the sum of the digits of 10^{50} - 74 ? We get: 1) the number of 9s will be exactly two fewer than the exponent on the 10, so: 10 ^{50} = (50 - 2) = 48 instances of the number 9 2) there will also be one 2 and one 6 3) the sum of the digits is (48 * 9) = 432 (that part takes care of summing the 9 s). Then add the 2 : (432 + 2) = 434. Then add the 6 and we are done. (434 + 6) = 440 Hope that helps.

*A fancy way to ask that question: If 10^{2} - 74 is written as an integer in base 10 notation, what is the sum of the digits in that integer? Does that help?

vishnusheth · Answer

For once I did it exactly the way Bunuel did it. I came up here to check if what I did was the right way and not only did I get it right but it's exactly the way Bunuel explained it. This is the first time in my almost a year's time on Gmatclub! I guess this calls for an ice-cream

ScottTargetTestPrep · Answer

Solution:

Consider a simpler version of the problem: 10^4 - 74. We see that 10^4 is the 5-digit number 10,000, and from it we subtract 74. The answer is a 4-digit number whose last 2 digits are 2 and 6, and all other digits are 9’s. In this case, the answer is 9926, and the sum of the digits is 9 + 9 + 2 + 6 = 26.

Similarly, 10^50 is a 51-digit number, and the difference 10^50 - 74 is a 50-digit number. The first 48 digits are 9, and the last two digits are 2 and 6. Therefore, the sum of the digits is 48 x 9 + 2 + 6 = 440.

Answer: C

darklord21 · Answer

A very simple approach to solve this problem would be to break down the terms into notations of 10
10^50 - (10^2-26)
(10^50 - 10^2) +26
10^2(10^48-1) + 26
100( 999.......48 times) + 26
(99999....48times 00) + 26
= 48*9 + 8
= 440 (C)

Oppenheimer1945 · Answer

1000-74=926

10^n-74=999...(n-2) times 26

10^50-74=9999...(48 times)26
Sum=48*9+8=(50-2)*9+8=450-10

ablatt4 · Answer

First instinct for me was to try and solve for the number which is too long to write out. If we remember that 10^1 has 1 0 after the 1 and 10^2 has 2 we can follow this pattern. 
By subtracting 26 we convert all of those 0s into 9s and the last 2 will be 100-74=26 which translates to 9(48) + 2+6.
9*50=450-9(2)=432+2+6=440

C is correct

ablatt4 · Answer

10^50 is just 1 followed by 50 0s, if we were to subtract 74 from that number all of those 0s would become 9s (to prove try it with 10^4-74) and the last 2 digits will be 100-74= 26 
If we have 50 total digits and 2 are not 9s the rest must be 9s therefore we have 48(9) +2+6 = 432+8 = 440

C

totaltestprepNick · Answer

C https://www.youtube.com/watch?v=IQpqmt5sOn0 Nick Slavkovich, GMAT/GRE tutor with 20+ years of experience tutoring@totaltestprep.net

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