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How many times will the digit 7 be written when listing the
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25 Dec 2019, 22:01
25 Dec 2019, 22:01
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64% (02:47) wrong based on 14 sessions
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How many times will the digit 7 be written when listing the integers from 1 to 1000?
A. 110
B. 111
C. 271
D. 300
E. 304
A. 110
B. 111
C. 271
D. 300
E. 304
Re: How many times will the digit 7 be written when listing the
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27 Dec 2019, 04:17
27 Dec 2019, 04:17
2
1
You can count numbers separately that their unit digit, tens digit and hundreds digit are equal to 7.
First, numbers that their units digit is 7: 7, 17, 27, ... ,997. There are 100 numbers [(997-7)/10+1].
Second, numbers that their tens digit is 7: 70,71, ..., 79 - 170,171,...,179 - ... - 970,971,...,979. There are 100 (10*10) numbers.
Third, numbers that their hundreds digit is 7: 700, 701, ..., 799. There are 100 numbers [(799-700)+1].
In total, the digit 7 will be written 300 times when listing the integers from 1 to 1000.
First, numbers that their units digit is 7: 7, 17, 27, ... ,997. There are 100 numbers [(997-7)/10+1].
Second, numbers that their tens digit is 7: 70,71, ..., 79 - 170,171,...,179 - ... - 970,971,...,979. There are 100 (10*10) numbers.
Third, numbers that their hundreds digit is 7: 700, 701, ..., 799. There are 100 numbers [(799-700)+1].
In total, the digit 7 will be written 300 times when listing the integers from 1 to 1000.
Re: How many times will the digit 7 be written when listing the
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01 Jun 2021, 06:10
01 Jun 2021, 06:10
Hello from the GRE Prep Club BumpBot!
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Thanks to another GRE Prep Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).
Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
