Mathematics

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Number System / संख्या पद्धति

Q36 2018, Number System

While writing all the numbers from 700 to 1000, how many numbers occur in which the digit at hundred's place is greater than the digit at ten's place, and the digit at ten's place is greater than the digit at unit's place?

यदि 700 से 1000 तक सभी संख्याएँ लिखी जाएँ, तो ऐसी कितनी संख्याएँ आती हैं जिनमें सैकड़े का अंक, दहाई के अंक से तथा दहाई का अंक, इकाई के अंक से बड़ा है?

Explanation Please wait..

For numbers from 700 to 1000, the digit at hundred's place can be 7, 8 or 9. So, three possibilities are there.

Now, for the digit at ten's place to be greater than the digit at unit's place, total numbers is equal to the value of ten's digit. For example, for 2 at ten's digit, numbers can be 20, 21 (total 2). Similarly, for 6 at ten's place, numbers can be 60, 61, 62, 63, 64, 65 (total 6).

When the first digit is 7, total numbers are = 1 + 2 + 3 + 4 + 5 + 6 = 21

When the first digit is 8, total numbers are = 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28

When the first digit is 9, total numbers are = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = 36

Therefore, required total numbers = 21 + 28 + 36 = 85.

<ul><li> 
For numbers from 700 to 1000,
the digit at hundred's place can be 7, 8 or 9. So, three possibilities are
there.</li></ul>

<ul><li> 
Now, for the digit at ten's
place to be greater than the digit at unit's place, total numbers is equal to
the value of ten's digit. For example, for 2 at ten's digit, numbers can be 20,
21 (total 2). Similarly, for 6 at ten's place, numbers can be 60, 61, 62, 63,
64, 65 (total 6). </li></ul>

<ul><li> 
When the first digit is 7,
total numbers are = 1 + 2 + 3 + 4 + 5 + 6 = 21</li></ul>

<ul><li> 
When the first digit is 8,
total numbers are = 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28</li></ul>

<ul><li> 
When the first digit is 9,
total numbers are = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = 36</li></ul>

<ul><li> 
Therefore, required total
numbers = 21 + 28 + 36 = 85.</li></ul>

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Mathematics

Q36 2018, Number System

While writing all the numbers from 700 to 1000, how many numbers occur in which the digit at hundred's place is greater than the digit at ten's place, and the digit at ten's place is greater than the digit at unit's place?

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John Doe

Mathematics

Q36 2018, Number System

While writing all the numbers from 700 to 1000, how many numbers occur in which the digit at hundred's place is greater than the digit at ten's place, and the digit at ten's place is greater than the digit at unit's place?

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व्याख्या Please wait..

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